[Titration curves of beta-lactamases using pH gradient electrophoresis]

The molecular relationships of two types of plasmid-mediated beta-lactamases, TEM-1 (R 111), TEM-2 (RP 4) and OXA-1 (RGN 238), OXA-4 (pMG 90) were analysed by combined isoelectrofocusing-electrophoresis. Titration curves of TEM-1 (pI 5.4) and TEM-2 (pI 5.6) together were consistent with the known substitution of a glutamic acid in the former by a lysin in the latter. When OXA-1 (pI 7.4) and OXA-4 (pI 7.45) were titrated, one single mobility curve was obtained reflecting their structural homogeneity. The titration curve technique will be usefull for the study of structure of beta-lactamases.