Carbohydrate Binding Module Family 1

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• Author:
• Responsible Curator: ^^^Markus Linder^^^

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CAZy DB link

http://www.cazy.org/CBM1.html

Ligand specificities

The family 1 CBMs are found in fungal enzymes only. Early work showed that family 1 CBMs bind to cellulose [1] and that some, but not all, family 1 CBMs bind to chitin as well [2]. There is also a contribution of CBMs in binding to lignin, but this binding was shown to be non-specific as it was easily blocked by surfactants [3]. Based on NMR measurements it was shown that family 1 CBMs could bind to cellohexaose, but not to shorter cellotrisoe and cellobiose [4].

Structural Features

Structurally the family 1 CBMs are distinct from other families. They are relatively small, only about 35 amino acids and have two or three disulphide bridges that stabilize their fold [5]. This type of fold is called a cystine knot and is also found in a family of toxins, called conotoxins produced by cone shells [6]. This structure is rigid and on the CMB there are three aromatic residues (tyrosines or tryptophans) that align so that their spacing is the same as every second pyranose ring on cellulose. Together with some hydrogen bond forming side chains this triad of aromatic residues form a binding face that docks onto the cellulose surface.

Functionalities

Content in this section should include, in paragraph form, a description of:

• Functional role of CBM: Describe common functional roles such as targeting, disruptive, anchoring, proximity/position on substrate.
• Most Common Associated Modules: 1. Glycoside Hydrolase Activity; 2. Additional Associated Modules (other CBM, FNIII, cohesin, dockerins, expansins, etc.)
• Novel Applications: Include here if CBM has been used to modify another enzyme, or if a CBM was used to label plant/mammalian tissues? Etc.

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Family 1 CBMs are found widely in fungal enzymes, also in several enzymes that are not active on cellulose such as mannanase [7] and acetyl xylan esterase [8]. Also swollenins have been found to contain family 1 CBMs [9]

Family Firsts

Family 1 CBMs were found first in studies on the Trichoderma reesei Cel7A enzyme (then called cellobiohydrolase I, CBHI) using papain for fragmentation. These studies revealed that Cel7A had a “bifunctional” organization with one part binding strongly to cellulose and the other part containing the catalytic machinery [10]. It was noted that homologous sequences to the smaller cellulose binding part was found in many fungal cellulases and that a synthetic analogue functioned identically to the native fragments produces by proteolysis [1]. The synthetic version of the cellulose binding domain was then analysed by NMR and its structure was determined [5]. With the structure determined the research then led to a number of structure-function studies identifying the amino acids responsible for binding [11] and changing of binding properties by protein engineering [12].

References

1. Johansson, G., Ståhlberg, J., Lindeberg, G., Engström, Å., Pettersson, G. (1989) Isolated Fungal Cellulose Terminal Domains and a Synthetic Minimum Analogue Bind to Cellulose. FEBS Lett. , 243, 389–393.

2. Linder M, Salovuori I, Ruohonen L, and Teeri TT. (1996). Characterization of a double cellulose-binding domain. Synergistic high affinity binding to crystalline cellulose. J Biol Chem. 1996;271(35):21268-72. DOI:10.1074/jbc.271.35.21268 |
3. Palonen H, Tjerneld F, Zacchi G, and Tenkanen M. (2004). Adsorption of Trichoderma reesei CBH I and EG II and their catalytic domains on steam pretreated softwood and isolated lignin. J Biotechnol. 2004;107(1):65-72. DOI:10.1016/j.jbiotec.2003.09.011 |

4. Mattinen, M. L.; Linder, M.; Teleman, A.; Annila, A. (1997) Interaction between Cellohexaose and Cellulose Binding Domains from Trichoderma Reesei Cellulases. FEBS Lett. 407, 291–296.

5. Kraulis J, Clore GM, Nilges M, Jones TA, Pettersson G, Knowles J, and Gronenborn AM. (1989). Determination of the three-dimensional solution structure of the C-terminal domain of cellobiohydrolase I from Trichoderma reesei. A study using nuclear magnetic resonance and hybrid distance geometry-dynamical simulated annealing. Biochemistry. 1989;28(18):7241-57. DOI:10.1021/bi00444a016 |

6. Norton, R. S.; Pallaghy, P. K. (1989) The Cystine Knot Structure of Ion Channel Toxins and Related Polypeptides. Toxicon 36, 1573–1583

10. van Tilbeurgh, H.; Tomme, P.; Claeyssens, M.; Bhikhabhai, R.; Pettersson, G. (1986) Limited Proteolysis of the c Ellobiohydrolase I from Trichoderma Reesei Separation of Functional Domains. FEBS Lett. 204, 223–227.

11. Linder, M.; Mattinen, M.-L.; Kontteli, M.; Lindeberg, G.; Ståhlberg, J.; Drakenberg, T.; Reinikainen, T.; Pettersson, Gör.; Annila, A. (1995) Identification of Functionally Important Amino Acids in the Cellulose-Binding Domain of Trichoderma Reesei Cellobiohydrolase I. Protein Sci. 4, 1056–1064.

12. Linder, M.; Nevanen, T.; Teeri, T. T. (1999) Design of a pH-Dependent Cellulose-Binding Domain. FEBS Lett. 447, 13–16.

13. PMID= 12199698