Missense mutations in the lacZ gene that result in degradation of beta-galactosidase structural protein.

Thirty-two missenese mutations were found among more than 200 independently induced mutations in the lacZ gene of Escherichia coli. Twenty of these missense mutations were induced by nitrosguandine, and 12 were induced by aminopurine. The lacZ structural protein was endogenously degradable in seven of the mutant strains; the mutations in these strains were found to lie at only three sites in the lacZ gene. Five of the seven independent mutations were at a single site, and some heterogeneity in the degradation of the lacZ protein was observed within these mutant strains.