Glycosyltransferase Family 138

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• Author: Wei Peng
• Responsible Curator: Kim Orth

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Glycosyltransferase Family GT138
Clan	Fido fold
Mechanism	Inverting
Active site residues	Known
CAZy DB link
https://www.cazy.org/GT138.html

Substrate specificities

GT138 family of glycosyltransferase is exemplified by AvrB [1]. As a bacterial effector from the plant pathogen Pseudomonas syringae, AvrB utilizes host UDP-rhamnose (or dTDP-rhamnose in vitro) as a co-substrate to modify the host protein RIN4 and causes the programmed cell death (namely hypersensitive response). AvrB that contains a Fido domain [2] (Fig. 1A), different from other known glycosyltransferases containing folds of GT-A, GT-B, GT-C, lysozyme-type, GT101, and GT108 (Fig. 1B). Interestingly, Fido proteins can also be enzymes with activities of AMPylation [3], phosphorylation [4], UMPylation [5], and phosphocholination [6, 7]. Therefore, AvrB is a unique Fido protein that functions as a glycosyltransferase.

Figure 1. Glycosyltransferase folds. (A) Fido fold (left [2]) is found in diverse enzymes including AvrB (right), which is a distinct glycosyltransferase. (B) Other known glycosyltransferases contain folds of GT-A, GT-B, GT-C, lysozyme-type, GT101, and GT108. PDB codes are provided for representative structures.

Kinetics and Mechanism

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Catalytic Residues

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Three-dimensional structures

AvrB represents the prototype for glycosyltransferases of Fido fold. AvrB contains a relatively large internal domain between helix α2 and helix α3 (Fig. 1A). Other Fido enzyme structures have been determined, though they have diverse activities as mentioned above. These Fido proteins share a similar fold while the primary sequences are divergent.

Family Firsts

First stereochemistry determination

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First catalytic nucleophile identification

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First general acid/base residue identification

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First 3-D structure

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References

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