Coordinated amino acid changes in homologous protein families

In the tobamovirus coat protein family, amino acid residuesat some spatially close positions are found to be substitutedin a coordinated manner [Altschuh et al. (1987) J. Mol. Biol.,193,693]. Therefore, these positions show an identical patternof amino acid substitutions when amino acid sequences of thesehomologous proteins are aligned. Based on this principle, coordinatedsubstitutions have been searched for in three additional proteinfamilies: serine proteases, cysteine proteases and the haemoglobins.Coordinated changes have been found in all three protein familiesmostly within structurally constrained regions. This methodworks with a varying degree of success depending on the functionof the proteins, the range of sequence similarities and thenumber of sequences considered. By relaxing the criteria forresidue selection, the method was adapted to cover a broaderrange of protein families and to study regions of the proteinshaving weaker structural constraints. The information derivedby these methods provides a general guide for engineering ofa large variety of proteins to analyse structure–functionrelationships.