Outer membrane of Escherichia coli K-12: differentiation of proteins 3A and 3B on acrylamide gels and further characterization of con (tolG) mutants

Abstract

Two classes of mutants, con and toiG, that appeared to be very similar in a number of respects have been shown to be identical and cotransducible with pyrD. By diethylaminoethyl-cellulose chromatography of the outer membranes, we have shown that the mutants are missing only protein 3A and retain protein 3B. Using con mutants, we were thus able to identify protein 3B on the pH 7.2 gel system of Maizel where it runs separately from protein 3A if unheated samples are used. tolG mutants were shown to be identical to con mutants in being conjugation defective with most F-like plasmid donors but not with I-like plasmid donors, and in their resistance pattern to bacteriophages and colicins.During the course ofthis study, it was observed that the bacteriocin produced by Serratia marcescens JF246 was identical in its activity spectrum to colicin L-398 and is now considered to be a colicin of type L.Recent studies of bacteriophage-and colicinresistant mutants ofEschericha coli have led to the identification of outer membrane proteins able to be used as receptors for these bacteriophages and colicins, and also to characterization of the biological role of the proteins.Sabet and Schnaitman (30) showed that bfe mutants, resistant to colicins El, E2, E3, and A and to bacteriophage BF23, have lost the receptor for at least some of these lethal agents and that this receptor is a protein involved in the transport of vitamin B12 (7). Bacteriophages Ti, T5, and 480 and colicin M also share a

Outer membrane proteins of Escherichia coli. VI. Protein alteration in bacteriophage-resistant mutants

“…These mutant strains were all selected for resistance to colicins or to lethal zygosis. Strain P460, which carries a mutation in ompA and produces no protein 3a (15), was sensitive to PA-2, and in fact showed a slightly higher plating efficiency for the phage than did the parent strain AB1133. Two strains that produce reduced amounts of protein 1 (P210, which has the phenotype TolIb, and JF568 tolF4) were still phage sensitive.…”

Further characterization of the recipient ability of Escherichia coli K-12 bacteriophage-resistant mutants

“…We showed previously (7) that among the set of bacteriophage-resistant mutants isolated by Hancock and Reeves (1) were a number of mutants defective as recipients in conjugation with an F' donor strain. We also demonstrated that the ompA mutants are defective as recipients with F', Hfr, and most F-like R-factor donors, but are competent with R100-1, the closely related R136fin-, and a number ofI-like R-factors including R64-11 (8). In this note we examine the remainder of these mutants for recipient ability with a strain carrying the I-like plasmid R64-11 and with an Hfr strain, to enable us to make more general comparisons.…”

“…and Hfr donors (7,8,11). ompA mutants are so markedly affected in their recipient ability that it seems that outer membrane protein 3A (absent in ompA mutants) plays an essential role in recipient functions for at least some F-like donors (7,8,11). Clearly, LPS also plays a role in recipient functions, but the role is apparently complex.…”

Cloned DNA fragment specifying major outer membrane protein a in Escherichia coli K-12

“…We speculate that some of these minor polypeptides may be processing and/or degradation products of the major polypeptides. The molecular weights of the pMC44specific polypeptides are approximately: Ml, 42,000; M2, 40,000; M4, 28,000; M5, 25,000.…”