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Crystal structure of the catalytic trimer of Methanococcus jannaschii aspartate transcarbamoylase
Author(s) -
Vitali Jacqueline,
Colaneri Michael J.,
Kantrowitz Evan
Publication year - 2007
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.21667
Subject(s) - methanococcus , trimer , aspartate carbamoyltransferase , crystal structure , crystallography , catalysis , chemistry , archaea , biochemistry , organic chemistry , dimer , escherichia coli , gene
The catalytic trimer of Methanococcus jannaschii aspartate transcarbamoylase is extremely heat stable, maintaining 75% of its activity after heat treatment for 60 min at 75°C. We undertook its structural analysis in order to understand the molecular basis of its thermostability and gain insight on how its catalytic function adapts to high temperature. Several structural elements potentially contributing to thermostability were identified. These include: (i) changes in the amino acid composition such as a decrease in the thermolabile residues Gln and Asn, an increase in the charged residues Lys and Glu, an increase in Tyr and a decrease in Ala residues; (ii) a larger number of salt bridges, in particular, the improvement of ion‐pair networks; (iii) shortening of the N‐terminus and shortening of three loops. An interesting feature of the crystal structure is the association of two crystallographically independent catalytic subunits into a staggered complex with an intertrimer distance of 33.8 Å. The active site appears similar to Escherichia coli. Upon substrate binding, smaller changes in the global orientation of domains and larger conformational changes of the active site residues are expected as compared to E. coli . Proteins 2008. © 2007 Wiley‐Liss, Inc.