Affiliation:
1. Laboratorium voor Erfelijkheidsleer en Microbiologie, Instituut voor Moleculaire Biologie en Biotechnologie, Vrije Universiteit Brussel en Vlaams Interuniversitair Instituut voor Biotechnologie, Brussels, Belgium.
Abstract
The genes coding for aspartate transcarbamylase (ATCase) in the deep-sea hyperthermophilic archaeon Pyrococcus abyssi were cloned by complementation of a pyrB Escherichia coli mutant. The sequence revealed the existence of a pyrBI operon, coding for a catalytic chain and a regulatory chain, as in Enterobacteriaceae. Comparison of primary sequences of the polypeptides encoded by the pyrB and pyrI genes with those of homologous eubacterial and eukaryotic chains showed a high degree of conservation of the residues which in E. coli ATCase are involved in catalysis and allosteric regulation. The regulatory chain shows more-extensive divergence with respect to that of E. coli and other Enterobacteriaceae than the catalytic chain. Several substitutions suggest the existence in P. abyssi ATCase of additional hydrophobic interactions and ionic bonds which are probably involved in protein stabilization at high temperatures. The catalytic chain presents a secondary structure similar to that of the E. coli enzyme. Modeling of the tridimensional structure of this chain provides a folding close to that of the E. coli protein in spite of several significant differences. Conservation of numerous pairs of residues involved in the interfaces between different chains or subunits in E. coli ATCase suggests that the P. abyssi enzyme has a quaternary structure similar to that of the E. coli enzyme. P. abyssi ATCase expressed in transgenic E. coli cells exhibited reduced cooperativity for aspartate binding and sensitivity to allosteric effectors, as well as a decreased thermostability and barostability, suggesting that in P. abyssi cells this enzyme is further stabilized through its association with other cellular components.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Reference86 articles.
1. Effects of salts on the aspartate transcarbamylase of a halophilic eubacterium, Vibrio costicola;Ahonkhai I.;Biochem. Cell. Biol.,1989
2. Decomposition of carbamylphosphate in aqueous solutions;Allen C. M. J.;Biochemistry,1964
3. Escherichia coli aspartate transcarbamoylase: structure, energetics, and catalytic and regulatory mechanisms. Annu;Allewell N. M.;Rev. Biophys. Biochem. Chem.,1989
4. Comparison of the aspartate transcarbamoylases from Serratia marcescens and Escherichia coli;Beck D.;J. Biol. Chem.,1989
5. Gene structure, organization, and expression in archaebacteria;Brown J. W.;Crit. Rev. Microbiol.,1989
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