Aspartate transcarbamylase from the deep-sea hyperthermophilic archaeon Pyrococcus abyssi: genetic organization, structure, and expression in Escherichia coli. Academic Article uri icon

Overview

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.

publication date

  • July 1, 1997

Research

keywords

  • Archaea
  • Aspartate Carbamoyltransferase
  • Bacterial Proteins

Identity

PubMed Central ID

  • PMC179233

Scopus Document Identifier

  • 0030873134

Digital Object Identifier (DOI)

  • 10.1128/jb.179.13.4143-4157.1997

PubMed ID

  • 9209027

Additional Document Info

volume

  • 179

issue

  • 13