ABSTRACT

We compare structural properties of the glycolytic enzymes 3-phosphoglycerate kinase (PGK; EC 2.7.2.3) and triosephosphate isomerase (TIM; EC 5.3.1.1) from mesophilic and hyperthermophilic Archaea to deduce common traits in protein thermoadaptation. PGKs and TIMs from Bacteria and Eucarya have been thoroughly investigated with respect to structure and function. For both enzymes, more than 30 amino acid sequences are known; the three-dimensional structure could be determined in four (PGK) or seven (TIM) cases, respectively. The PGKs of eucaryal and bacterial sources represent monomeric enzymes and exhibit a bilobal structure (Blake and Evans, 1974; Watson et al., 1982; Harlos et al., 1992; Davies et al., 1993). For its catalytic activity, an induced-fit mechanism with excessive hinge bending has been proposed (Sinev et al., 1989; Haran et al., 1992), which has recently been confirmed by crystal analysis of the closed conformation (Bernstein et al., 1997).