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Carbohydrate Binding Module Family 19

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CAZy DB link
http://www.cazy.org/CBMnn.html

Ligand specificities

The CBM19 found in the CTS1 chitinase produced by Saccharomyces cerevisiae has been characterized as a chitin-binding CBM [1]. The authors produced several manipulated constructs in yeast to demonstrate chitin binding including making a C-terminal deletion mutant, controlled proteolysis of the wild-type enzyme, production of only the C-terminal CBM11 with the N-terminal signal sequence and fusion of the CBM19 with the yeast invertase SUC2 [1]. These different constructs were then tested for their chitin-binding capabilities. The CBM19 is suggested to bind with high affinity, though no binding affinity was experimentally determined [1]. Interestingly, the C-terminal deletion mutant showed an enhanced rate of chitin hydrolysis relative to the wild type.


Structural Features

Two alleles of the cts1 gene have been identified, they are referred to as cts1-1 and cts1-2 [1]. The predicted full length protein is likely divided into four domains [1]. The first domain (amino acids 1-20) is the cleavable signal sequence, the second domain is the chitinase GH18 catalytic domain (amino acids 21-327), the third domain is a highly glycosylated serine/threonine-rich domain (amino acids 328-480) and the fourth domain is the chitin binding CBM19 [1, 2].

There is no 3D structure available for the CBM19 family.


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

  • Fold: Structural fold (beta trefoil, beta sandwich, etc.)
  • Type: Include here Type A, B, or C and properties
  • Features of ligand binding: Describe CBM binding pocket location (Side or apex) important residues for binding (W, Y, F, subsites), interact with reducing end, non-reducing end, planar surface or within polysaccharide chains. Include examples pdb codes. Metal ion dependent. Etc.

Functionalities

Chitin is an important component of the cell wall of Saccharomyces cerevisiae. It is specifically located at the junction of mother and daughter cells providing mechanical stability. The CTS1 enzyme, containing a GH18 catalytic module is produced by S. cerevisiae and hydrolyses chitin[3, 4] and has a role in cell separation [1]. When chitinase activity was disrupted cells were unable to separate normally resulting in aggregates of cells connected by their cell septum regions [1]. Complementation experiments were able to restore the separation phenotype with plasmids containing cts1-1 or cts1-2; however, the C-terminal deletion mutant only partly restores the phenotype [1]. This suggests the CBM19 is involved in the mechanism of cell separation between mother and daughter cells.

Family Firsts

First Identified
The chitin-binding CBM19 from CTS1 in Saccharomyces cerevisiae was first described by Kuranda and Robbins in 1991 [1].
First Structural Characterization
There is no 3D structural data on the CBM19 family.

References

  1. Kuranda MJ and Robbins PW. (1991). Chitinase is required for cell separation during growth of Saccharomyces cerevisiae. J Biol Chem. 1991;266(29):19758-67. | Google Books | Open Library PubMed ID:1918080 [Kuranda1991]
  2. Lombard V, Golaconda Ramulu H, Drula E, Coutinho PM, and Henrissat B. (2014). The carbohydrate-active enzymes database (CAZy) in 2013. Nucleic Acids Res. 2014;42(Database issue):D490-5. DOI:10.1093/nar/gkt1178 | PubMed ID:24270786 [Lombard2014]
  3. Correa JU, Elango N, Polacheck I, and Cabib E. (1982). Endochitinase, a mannan-associated enzyme from Saccharomyces cerevisiae. J Biol Chem. 1982;257(3):1392-7. | Google Books | Open Library PubMed ID:6799506 [Correa1982]
  4. Kuranda MJ and Robbins PW. (1987). Cloning and heterologous expression of glycosidase genes from Saccharomyces cerevisiae. Proc Natl Acad Sci U S A. 1987;84(9):2585-9. DOI:10.1073/pnas.84.9.2585 | PubMed ID:3033651 [Kuranda1987]

All Medline abstracts: PubMed