Carbohydrate Binding Module Family 102 - Revision history

Marie-Katherin Zuehlke at 10:23, 7 November 2024

2024-11-07T10:23:18Z

Marie-Katherin Zuehlke: /* Ligand specificities */

2024-11-07T10:20:12Z

Ligand specificities

Marie-Katherin Zuehlke: /* Structural Features */

2024-11-07T10:19:13Z

Structural Features

Marie-Katherin Zuehlke at 09:45, 7 November 2024

2024-11-07T09:45:58Z

Elizabeth Ficko-Blean at 14:34, 25 October 2024

2024-10-25T14:34:15Z

Elizabeth Ficko-Blean at 14:19, 25 October 2024

2024-10-25T14:19:38Z

Elizabeth Ficko-Blean at 14:17, 25 October 2024

2024-10-25T14:17:09Z

Elizabeth Ficko-Blean at 14:11, 25 October 2024

2024-10-25T14:11:32Z

Elizabeth Ficko-Blean at 09:58, 13 September 2024

2024-09-13T09:58:25Z

Elizabeth Ficko-Blean at 09:56, 13 September 2024

2024-09-13T09:56:14Z

@@ Line 23: / Line 23: @@
 The CBM102 displays a β-sandwich fold established by two antiparallel β-sheets forming a convex and a concave face. The 3D X-ray crystal structure of the C-terminal CBM102<sub>IV</sub> of the ''C. forsetii'' SGBP showed that, together with two expansive loops, the concave face provides a narrow cleft to accommodate laminaritriose <cite>Zuehlke2024</cite> (Figure 1b). CBM102 thus represents a [[Carbohydrate-binding_modules|type B CBM]]. Three residues located in the concave face mediate polar interactions with laminaritriose (Lys825, Glu827 and Glu837), while one aromatic residue of each loop (Tyr790, Phe861) is involved in CH-π interaction with the ligand (Figure 1c). However, the ''C. forsetii'' protein contains three additional CBM102s. Alphafold2 <cite>Mirdita2022</cite> predictions showed that two of them are highly similar to the 3D crystal structure of the C-terminal CBM102<sub>IV</sub>, but that one CBM102 is missing one of the loops shaping the pocket, which results in a very shallow cleft (Figure 2). This was speculated to represent an adaptation to highly branched laminarins <cite>Zuehlke2024</cite>.
-[[File:FigSGBP.png|thumb|'''Figure 1.''' '''a''' The Alphafold2-predicted structure of the CBM102-containing SGBP of ''C. forsetii'' <cite>Zuehlke2024</cite>. The four CBM102s (I-IV, red) follow two N-terminal Ig-like domains (grey). '''b''' 3D crystal structure of the C-terminal CBM102<sub>IV</sub> of the ''C. forsetii'' SGBP with laminaritriose (PDB ID [https://www.rcsb.org/structure/unreleased/8QX6 8QX6]) <cite>Zuehlke2024</cite>. '''c''' Zooming into the binding site: residues mediating polar and CH-π interactions with laminaritriose.]]
+[[File:FigSGBP.png|thumb|'''Figure 1.''' '''a''' The Alphafold2-predicted structure of the CBM102-containing SGBP of ''C. forsetii'' <cite>Zuehlke2024</cite>. The four CBM102s (I-IV, red) follow two N-terminal Ig-like domains (grey). '''b''' 3D crystal structure of the C-terminal CBM102<sub>IV</sub> of the ''C. forsetii'' SGBP with laminaritriose (PDB ID [https://www.rcsb.org/structure/8QX6 8QX6]) <cite>Zuehlke2024</cite>. '''c''' Zooming into the binding site: residues mediating polar and CH-π interactions with laminaritriose.]]
-[[File:CBM102s.png|thumb|'''Figure 2.''' Surfaces of the four CBM102s of the ''C. forsetii'' SGBP  <cite>Zuehlke2024</cite>. Left: 3D crystal structure of the C-terminal CBM102<sub>IV</sub> with laminaritriose (PDB ID [https://www.rcsb.org/structure/unreleased/8QX6 8QX6]). Right: Alphafold2-predicted structures (I-III). CBM102<sub>III</sub> is missing one of the groove-forming loops.]]
+[[File:CBM102s.png|thumb|'''Figure 2.''' Surfaces of the four CBM102s of the ''C. forsetii'' SGBP  <cite>Zuehlke2024</cite>. Left: 3D crystal structure of the C-terminal CBM102<sub>IV</sub> with laminaritriose (PDB ID [https://www.rcsb.org/structure/8QX6 8QX6]). Right: Alphafold2-predicted structures (I-III). CBM102<sub>III</sub> is missing one of the groove-forming loops.]]
 == Functionalities ==
@@ Line 32: / Line 32: @@
 == Family Firsts ==
 ;First Identified: CBM102 was first identified in an SGBP encoded in a laminarin utilization locus of ''Christiangramia forsetii'' KT0803<sup>T</sup> <cite>Zuehlke2024</cite>, a marine flavobacterium isolated from surface waters in the North Sea <cite>Eilers2001</cite>. More than 350 CBM102-containing sequences were detected in bacterial metagenome-assembled genomes (555 representative MAGs of which 201 belonged to ''Bacteroidota'') retrieved from bacterial biomass from phytoplankton blooms of three respective years (2016, 2018 and 2020) in the North Sea. Sequences mostly belonged to Bacteroidota, but also to ''Proteobacteria'', ''Myxococcota'' and ''Actinobacteriota'' <cite>Zuehlke2024</cite>. The association with GHs (mostly [[GH16]]_3) within this dataset led to the creation of the CBM family 102.
-;First Structural Characterization: The C-terminal CBM102<sub>IV</sub> of the laminarin PUL-encoded SGBP of ''C. forsetii'' KT0803<sup>T</sup> is the first structurally characterized member of the family (PDB ID [https://www.rcsb.org/structure/unreleased/8QX6 8QX6]). The 3D crystal structure was obtained in complex with laminaritriose.
+;First Structural Characterization: The C-terminal CBM102<sub>IV</sub> of the laminarin PUL-encoded SGBP of ''C. forsetii'' KT0803<sup>T</sup> is the first structurally characterized member of the family (PDB ID [https://www.rcsb.org/structure/8QX6 8QX6]). The 3D crystal structure was obtained in complex with laminaritriose.
 == References ==

@@ Line 18: / Line 18: @@
 == Ligand specificities ==
-The dissected C-terminal CBM102<sub>IV</sub> of a surface glycan-binding protein (SGBP; containing four CBM102s I-IV) of ''Christiangramia forsetii'' KT0803<sup>T</sup> binds laminarin (from ''Laminaria digitata'') and laminarin-derived oligosaccharides as determined by affinity gel electrophoresis and/or isothermal titration calorimetry <cite>Zuehlke2024</cite>.  CBM102<sub>IV</sub> has a higher affinity to laminarin (K<sub>a</sub> ~1.04 x 10<sup>5</sup> M<sup>-1</sup>) than to laminariheptaose (K<sub>a</sub> ~1.87 x 10<sup>4</sup> M<sup>-1</sup>) and laminaripentaose (K<sub>a</sub> ~1.39 x 10<sup>4</sup> M<sup>-1</sup>). Laminaribiose did not bind the CBM102<sub>IV</sub>. In addition, the dissected C-terminal CBM102<sub>IV</sub> has a higher affinity to laminarin than two CBM102 tandem constructs of the SGBP (K<sub>a</sub> ~2.76 x 10<sup>4</sup> M<sup>-1</sup> or ~3.63 x 10<sup>4</sup> M<sup>-1</sup>) and the full length SGBP (K<sub>a</sub> ~3.09 x 10<sup>4</sup> M<sup>-1</sup>) <cite>Zuehlke2024</cite>.
+The dissected C-terminal CBM102<sub>IV</sub> of a surface glycan-binding protein (SGBP; containing four CBM102s I-IV, Figure 1a) of ''Christiangramia forsetii'' KT0803<sup>T</sup> binds laminarin (from ''Laminaria digitata'') and laminarin-derived oligosaccharides as determined by affinity gel electrophoresis and/or isothermal titration calorimetry <cite>Zuehlke2024</cite>.  CBM102<sub>IV</sub> has a higher affinity to laminarin (K<sub>a</sub> ~1.04 x 10<sup>5</sup> M<sup>-1</sup>) than to laminariheptaose (K<sub>a</sub> ~1.87 x 10<sup>4</sup> M<sup>-1</sup>) and laminaripentaose (K<sub>a</sub> ~1.39 x 10<sup>4</sup> M<sup>-1</sup>). Laminaribiose did not bind the CBM102<sub>IV</sub>. In addition, the dissected C-terminal CBM102<sub>IV</sub> has a higher affinity to laminarin than two CBM102 tandem constructs of the SGBP (K<sub>a</sub> ~2.76 x 10<sup>4</sup> M<sup>-1</sup> or ~3.63 x 10<sup>4</sup> M<sup>-1</sup>) and the full length SGBP (K<sub>a</sub> ~3.09 x 10<sup>4</sup> M<sup>-1</sup>) <cite>Zuehlke2024</cite>.
 == Structural Features ==

@@ Line 21: / Line 21: @@
 == Structural Features ==
-The CBM102 displays a β-sandwich fold established by two antiparallel β-sheets forming a convex and a concave face. The 3D X-ray crystal structure of the C-terminal CBM102<sub>IV</sub> of the ''C. forsetii'' SGBP showed that, together with two expansive loops, the concave face provides a narrow cleft to accommodate laminaritriose <cite>Zuehlke2024</cite> (Figure 1). CBM102 thus represents a [[Carbohydrate-binding_modules|type B CBM]]. Three residues located in the concave face mediate polar interactions with laminaritriose (Lys825, Glu827 and Glu837), while one aromatic residue of each loop (Tyr790, Phe861) is involved in CH-π interaction with the ligand. However, the ''C. forsetii'' protein contains three additional CBM102s. Alphafold2 <cite>Mirdita2022</cite> predictions showed that two of them are highly similar to the 3D crystal structure of the C-terminal CBM102<sub>IV</sub>, but that one CBM102 is missing one of the loops shaping the pocket, which results in a very shallow cleft (Figure 2). This was speculated to represent an adaptation to highly branched laminarins <cite>Zuehlke2024</cite>.
+The CBM102 displays a β-sandwich fold established by two antiparallel β-sheets forming a convex and a concave face. The 3D X-ray crystal structure of the C-terminal CBM102<sub>IV</sub> of the ''C. forsetii'' SGBP showed that, together with two expansive loops, the concave face provides a narrow cleft to accommodate laminaritriose <cite>Zuehlke2024</cite> (Figure 1b). CBM102 thus represents a [[Carbohydrate-binding_modules|type B CBM]]. Three residues located in the concave face mediate polar interactions with laminaritriose (Lys825, Glu827 and Glu837), while one aromatic residue of each loop (Tyr790, Phe861) is involved in CH-π interaction with the ligand (Figure 1c). However, the ''C. forsetii'' protein contains three additional CBM102s. Alphafold2 <cite>Mirdita2022</cite> predictions showed that two of them are highly similar to the 3D crystal structure of the C-terminal CBM102<sub>IV</sub>, but that one CBM102 is missing one of the loops shaping the pocket, which results in a very shallow cleft (Figure 2). This was speculated to represent an adaptation to highly branched laminarins <cite>Zuehlke2024</cite>.
-[[File:Fig.1.png|thumb|'''Figure 1.''' 3D crystal structure of the C-terminal CBM102<sub>IV</sub> of the ''C. forsetii'' SGBP with laminaritriose (PDB ID [https://www.rcsb.org/structure/unreleased/8QX6 8QX6]) <cite>Zuehlke2024</cite>. Highlighted are interacting residues.]]
+[[File:FigSGBP.png|thumb|'''Figure 1.''' '''a''' The Alphafold2-predicted structure of the CBM102-containing SGBP of ''C. forsetii'' <cite>Zuehlke2024</cite>. The four CBM102s (I-IV, red) follow two N-terminal Ig-like domains (grey). '''b''' 3D crystal structure of the C-terminal CBM102<sub>IV</sub> of the ''C. forsetii'' SGBP with laminaritriose (PDB ID [https://www.rcsb.org/structure/unreleased/8QX6 8QX6]) <cite>Zuehlke2024</cite>. '''c''' Zooming into the binding site: residues mediating polar and CH-π interactions with laminaritriose.]]
 == Functionalities ==
 The CBM102-containing SGBP is tethered to the outer membrane of ''C. forsetii'' and is abundantly produced in laminarin-grown cells <cite>Kabisch2014</cite>. With four CBM102s, the SGBP provides multiple laminarin docking sites <cite>Zuehlke2024</cite>. The protein further contains two N-terminal Ig-like domains that precede the CBM102s, which presumably act as spacers to ensure distance to the membrane and exposure of binding sites as suggested before for β-glucan-binding CBM-containing SGBPs <cite>Tamura2021</cite>. The four repeating CBM102s in the ''C. forsetii'' protein were suggested to render the SGBP an optimal 'sugar-trapping antenna' on the bacterial surface; this is supported by an elongated protein shape (''R''<sub>g</sub> 52 Å and ''D''<sub>max</sub> 178 Å) as determined by small angle X-ray scattering <cite>Zuehlke2024</cite>. Unexpectedly, isothermal titration calorimetry showed that maximum two laminarin molecules were bound by the four CBM102s and that affinity was not increased by multiple CBM102s. In bacterial metagenome-assembled genomes from phytoplankton blooms in the North Sea, CBM102 was detected together with appended catalytic modules, indicating other putative functions (for example enhancing enzyme concentration on substrate to improve catalysis) <cite>Zuehlke2024</cite>. The majority of associated catalytic modules were [[GH16]]_3s, but also rare examples of [[Glycoside_Hydrolase_Family_2|GH2]], [[GH5]]_34, [[Glycoside_Hydrolase_Family_81|GH81]], and [[Glycoside_Hydrolase_Family_162|GH162]]. Within this dataset, CBM102 also co-occurred with [[Carbohydrate_Binding_Module_Family_4|CBM4]], [[Carbohydrate_Binding_Module_Family_6|CBM6]] and [[Carbohydrate_Binding_Module_Family_103|CBM103]] in multimodular proteins. CBM102-only-proteins contained up to eight repeats of CBM102. The production of CBM102-containing proteins correlated with the course of the phytoplankton bloom, which underlines the relevance of CBM102 in marine β-glucan use.

@@ Line 18: / Line 18: @@
 == Ligand specificities ==
-The dissected C-terminal CBM102<sub>IV</sub> of a surface glycan-binding protein (SGBP; containing four CBM102s I-IV) of ''Christiangramia forsetii'' KT0803<sup>T</sup> binds laminarin (from ''Laminaria digitata'') and laminarin-derived oligosaccharides- as determined by affinity gel electrophoresis and/or isothermal titration calorimetry <cite>Zuehlke2024</cite>.  CBM102<sub>IV</sub> has a higher affinity to laminarin (K<sub>a</sub> ~1.04 x 10<sup>5</sup> M<sup>-1</sup>) than to laminariheptaose (K<sub>a</sub> ~1.87 x 10<sup>4</sup> M<sup>-1</sup>) and laminaripentaose (K<sub>a</sub> ~1.39 x 10<sup>4</sup> M<sup>-1</sup>). Laminaribiose did not bind the CBM102<sub>IV</sub>. In addition, the dissected C-terminal CBM102<sub>IV</sub> has a higher affinity to laminarin than two CBM102 tandem constructs of the SGBP (K<sub>a</sub> ~2.76 x 10<sup>4</sup> M<sup>-1</sup> or ~3.63 x 10<sup>4</sup> M<sup>-1</sup>) and the full length SGBP (K<sub>a</sub> ~3.09 x 10<sup>4</sup> M<sup>-1</sup>) <cite>Zuehlke2024</cite>.
+The dissected C-terminal CBM102<sub>IV</sub> of a surface glycan-binding protein (SGBP; containing four CBM102s I-IV) of ''Christiangramia forsetii'' KT0803<sup>T</sup> binds laminarin (from ''Laminaria digitata'') and laminarin-derived oligosaccharides as determined by affinity gel electrophoresis and/or isothermal titration calorimetry <cite>Zuehlke2024</cite>.  CBM102<sub>IV</sub> has a higher affinity to laminarin (K<sub>a</sub> ~1.04 x 10<sup>5</sup> M<sup>-1</sup>) than to laminariheptaose (K<sub>a</sub> ~1.87 x 10<sup>4</sup> M<sup>-1</sup>) and laminaripentaose (K<sub>a</sub> ~1.39 x 10<sup>4</sup> M<sup>-1</sup>). Laminaribiose did not bind the CBM102<sub>IV</sub>. In addition, the dissected C-terminal CBM102<sub>IV</sub> has a higher affinity to laminarin than two CBM102 tandem constructs of the SGBP (K<sub>a</sub> ~2.76 x 10<sup>4</sup> M<sup>-1</sup> or ~3.63 x 10<sup>4</sup> M<sup>-1</sup>) and the full length SGBP (K<sub>a</sub> ~3.09 x 10<sup>4</sup> M<sup>-1</sup>) <cite>Zuehlke2024</cite>.
 == Structural Features ==
@@ Line 27: / Line 27: @@
 [[File:Fig.2.png|thumb|'''Figure 2.''' Surfaces of the four CBM102s of the ''C. forsetii'' SGBP  <cite>Zuehlke2024</cite>. Left: 3D crystal structure of the C-terminal CBM102<sub>IV</sub> with laminaritriose (PDB ID [https://www.rcsb.org/structure/unreleased/8QX6 8QX6]). Right: Alphafold2-predicted structures (I-III). CBM102<sub>III</sub> is missing one of the groove-forming loops.]]
 == Functionalities ==
-The CBM102-containing SGBP is tethered to the outer membrane of ''C. forsetii'' and is abundantly produced in laminarin-grown cells <cite>Kabisch2014</cite>. With four CBM102s, the SGBP provides multiple laminarin docking sites <cite>Zuehlke2024</cite>. The protein further contains two N-terminal Ig-like domains that precede the CBM102s, which presumably act as spacers to ensure distance to the membrane and exposure of binding sites as suggested before for β-glucan-binding CBM-containing SGBPs <cite>Tamura2021</cite>. The four repeating CBM102s in the ''C. forsetii'' protein were suggested to render the SGBP an optimal 'sugar-trapping antenna' on the bacterial surface; this is supported by an elongated protein shape as determined by small angle X ray scattering <cite>Zuehlke2024</cite>. Unexpectedly, isothermal titration calorimetry showed that maximum two laminarin molecules were bound by the four CBM102s and that affinity was not increased by multiple CBM102s. In bacterial metagenome-assembled genomes from phytoplankton blooms in the North Sea, CBM102 was detected together with appended catalytic modules, indicating other putative functions (for example enhancing enzyme concentration on substrate to improve catalysis) <cite>Zuehlke2024</cite>. The majority of associated catalytic modules were [[GH16]]_3s, but also rare examples of [[Glycoside_Hydrolase_Family_2|GH2]], [[GH5]]_34, [[Glycoside_Hydrolase_Family_81|GH81]], and [[Glycoside_Hydrolase_Family_162|GH162]]. Within this dataset, CBM102 also co-occurred with [[Carbohydrate_Binding_Module_Family_4|CBM4]], [[Carbohydrate_Binding_Module_Family_6|CBM6]] and [[Carbohydrate_Binding_Module_Family_103|CBM103]] in multimodular proteins. CBM102-only-proteins contained up to eight repeats of CBM102. The production of CBM102-containing proteins correlated with the course of the phytoplankton bloom, which underlines the relevance of CBM102 in marine β-glucan use.
+The CBM102-containing SGBP is tethered to the outer membrane of ''C. forsetii'' and is abundantly produced in laminarin-grown cells <cite>Kabisch2014</cite>. With four CBM102s, the SGBP provides multiple laminarin docking sites <cite>Zuehlke2024</cite>. The protein further contains two N-terminal Ig-like domains that precede the CBM102s, which presumably act as spacers to ensure distance to the membrane and exposure of binding sites as suggested before for β-glucan-binding CBM-containing SGBPs <cite>Tamura2021</cite>. The four repeating CBM102s in the ''C. forsetii'' protein were suggested to render the SGBP an optimal 'sugar-trapping antenna' on the bacterial surface; this is supported by an elongated protein shape (''R''<sub>g</sub> 52 Å and ''D''<sub>max</sub> 178 Å) as determined by small angle X-ray scattering <cite>Zuehlke2024</cite>. Unexpectedly, isothermal titration calorimetry showed that maximum two laminarin molecules were bound by the four CBM102s and that affinity was not increased by multiple CBM102s. In bacterial metagenome-assembled genomes from phytoplankton blooms in the North Sea, CBM102 was detected together with appended catalytic modules, indicating other putative functions (for example enhancing enzyme concentration on substrate to improve catalysis) <cite>Zuehlke2024</cite>. The majority of associated catalytic modules were [[GH16]]_3s, but also rare examples of [[Glycoside_Hydrolase_Family_2|GH2]], [[GH5]]_34, [[Glycoside_Hydrolase_Family_81|GH81]], and [[Glycoside_Hydrolase_Family_162|GH162]]. Within this dataset, CBM102 also co-occurred with [[Carbohydrate_Binding_Module_Family_4|CBM4]], [[Carbohydrate_Binding_Module_Family_6|CBM6]] and [[Carbohydrate_Binding_Module_Family_103|CBM103]] in multimodular proteins. CBM102-only-proteins contained up to eight repeats of CBM102. The production of CBM102-containing proteins correlated with the course of the phytoplankton bloom, which underlines the relevance of CBM102 in marine β-glucan use.
 == Family Firsts ==
-;First Identified: CBM102 was first identified in an SGBP encoded in a laminarin utilization locus of ''Christiangramia forsetii'' KT0803<sup>T</sup> <cite>Zuehlke2024</cite>, a marine flavobacterium isolated from surface waters in the North Sea <cite>Eilers2001</cite>. More than 350 CBM102-containing sequences were detected in bacterial metagenome-assembled genomes (555 representative MAGs of which 201 belonged to ''Bacteroidota'') retrieved from bacterial biomass from phytoplankton blooms of three respective years (2016, 2018 and 2020) in the North Sea. Sequences mostly belonged to Bacteroidota, but also to Proteobacteria, Myxococcota and Actinobacteriota <cite>Zuehlke2024</cite>. The association with GHs (mostly [[GH16]]_3) within this dataset led to the creation of the CBM family 102.
+;First Identified: CBM102 was first identified in an SGBP encoded in a laminarin utilization locus of ''Christiangramia forsetii'' KT0803<sup>T</sup> <cite>Zuehlke2024</cite>, a marine flavobacterium isolated from surface waters in the North Sea <cite>Eilers2001</cite>. More than 350 CBM102-containing sequences were detected in bacterial metagenome-assembled genomes (555 representative MAGs of which 201 belonged to ''Bacteroidota'') retrieved from bacterial biomass from phytoplankton blooms of three respective years (2016, 2018 and 2020) in the North Sea. Sequences mostly belonged to Bacteroidota, but also to ''Proteobacteria'', ''Myxococcota'' and ''Actinobacteriota'' <cite>Zuehlke2024</cite>. The association with GHs (mostly [[GH16]]_3) within this dataset led to the creation of the CBM family 102.
 ;First Structural Characterization: The C-terminal CBM102<sub>IV</sub> of the laminarin PUL-encoded SGBP of ''C. forsetii'' KT0803<sup>T</sup> is the first structurally characterized member of the family (PDB ID [https://www.rcsb.org/structure/unreleased/8QX6 8QX6]). The 3D crystal structure was obtained in complex with laminaritriose.

@@ Line 1: / Line 1: @@
 <!-- RESPONSIBLE CURATORS: Please replace the {{UnderConstruction}} tag below with {{CuratorApproved}} when the page is ready for wider public consumption -->
-{{UnderConstruction}}
+{{CuratorApproved}}
 * [[Author]]: [[User:Marie-Katherin Zuehlke|Marie-Katherin Zühlke]]
 * [[Responsible Curator]]:  [[User:Elizabeth Ficko-Blean|Elizabeth Ficko-Blean]]

@@ Line 21: / Line 21: @@
 == Structural Features ==
-The CBM102 displays a β-sandwich fold established by two antiparallel β-sheets forming a convex and a concave face. The 3D X-ray crystal structure of the C-terminal CBM102 of the ''C. forsetii'' SGBP showed that together with two expansive loops, the concave face provides a narrow cleft to accommodate laminaritriose <cite>Zuehlke2024</cite> (Figure 1). CBM102 thus represents a [[Carbohydrate-binding_modules|type B CBM]]. Three residues located in the concave face mediate polar interactions with laminaritriose (Lys825, Glu827 and Glu837), while one aromatic residue of each loop (Tyr790, Phe861) is involved in CH-π interaction with the ligand. However, the ''C. forsetii'' protein contains three additional CBM102s. Alphafold2 <cite>Mirdita2022</cite> predictions showed that two of them are highly similar to the 3D crystal structure of the C-terminal CBM102, but that one CBM102 is missing one of the loops shaping the pocket, which results in a very shallow cleft (Figure 2). This was speculated to represent an adaptation to highly branched laminarins <cite>Zuehlke2024</cite>.
+The CBM102 displays a β-sandwich fold established by two antiparallel β-sheets forming a convex and a concave face. The 3D X-ray crystal structure of the C-terminal CBM102 of the ''C. forsetii'' SGBP showed that, together with two expansive loops, the concave face provides a narrow cleft to accommodate laminaritriose <cite>Zuehlke2024</cite> (Figure 1). CBM102 thus represents a [[Carbohydrate-binding_modules|type B CBM]]. Three residues located in the concave face mediate polar interactions with laminaritriose (Lys825, Glu827 and Glu837), while one aromatic residue of each loop (Tyr790, Phe861) is involved in CH-π interaction with the ligand. However, the ''C. forsetii'' protein contains three additional CBM102s. Alphafold2 <cite>Mirdita2022</cite> predictions showed that two of them are highly similar to the 3D crystal structure of the C-terminal CBM102, but that one CBM102 is missing one of the loops shaping the pocket, which results in a very shallow cleft (Figure 2). This was speculated to represent an adaptation to highly branched laminarins <cite>Zuehlke2024</cite>.
 [[File:Fig.1.png|thumb|'''Figure 1.''' 3D crystal structure of the C-terminal CBM102 of the ''C. forsetii'' SGBP with laminaritriose (PDB ID [https://www.rcsb.org/structure/unreleased/8QX6 8QX6]) <cite>Zuehlke2024</cite>. Highlighted are interacting residues.]]