PROBING THE DETERMINANTS OF PROTEIN STABILITY - COMPARISON OF CLASS-ABETA-LACTAMASES

Five class A beta-lactamases produced by various mesophilic bacterial species have been compared. Although closely related in primary and ov erall structures, these enzymes exhibit very different stabilities. In order to investigate the factors responsible for these differences, s everal features deduced from the amino acid composition and three-dime nsional structures were studied for the five proteins. This analysis r evealed that higher stability appeared to correlate with increased num bers of intramolecular hydrogen bonds and of salt bridges. By contrast , the global hydrophobicity of the protein seemed to play a relatively minor role. A strongly unfavourable balance between charged residues and the presence of a cis-peptide bond preceding a non-proline residue might also contribute to the particularly low stability of two of the enzymes.