Autogenous regulation by wild-type and mutant L4 proteins. (A) Maps of plasmids. The source plasmid carries the L4 gene under control of an arabinose-inducible promoter. The target plasmid contains the S10 leader and S10′/′lacZ fusion gene under control of an IPTG-inducible promoter. (B) Effect of L4 oversynthesis on S10′/′β-gal synthesis. Cells induced with IPTG (−) or IPTG and arabinose (+) were pulse-labeled with [35S]methionine and analyzed by gel electrophoresis and PhosphorImager quantitation. The effect of a given L4 on fusion protein synthesis (+L4/−L4) was calculated as described in Materials and Methods. Values shown are the average of all experiments for a given L4, whether or not it had a tag (n = 4–8). Standard deviations are in parentheses.
