Secondary Structure Relations Between Beta‐lactamases and Penicillin‐sensitive D—alanine—carboxypeptidases

The sequence homology found by Waxman & Strominger between penicillin-sensitive D-alanine-carboxypeptidases and penicillin-inactivating beta-lactamases is shown to extend to the level of secondary structure as predicted by the method of Chou & Fasman or by the informational method of Garnier et al. Thermodynamic similarity of homologous segments of these proteins is demonstrated by means of a sequence-independent parameter, the hydration potential of Wolfenden at al. Although the 40- to 70-residue amino-terminal sequences examined contain a common serine reactive with penicillins and (in the case of the carboxypeptidases) an R-D-alanyl-D-alanine substrate analog, no homology in secondary structure or hydration potential could be found with a serine protease such as alpha-chymotrypsin.