Isolation andCharacterization ofChain-Terminating Nonsense Mutations ina Porin Regulator Gene,envZ

We isolated fourindependent ambermutations ingeneenvZ, whoseproduct is involved intheregulation ofporinprotein genesompFandompC.TheenvZ amberstrains exhibit an OmpF-l' OmpC-porin phenotype andexpressother envelope protein genesatwild-type levels. Thisphenotype isclearly different fromthatofthepreviously isolated class ofenvZmutants thatexhibit anOmpFOmpC+ phenotype anda pleiotropic decrease intheexpression ofseveral exported protein genes,including lamBandphoA.Theaddition ofthelocal anesthetic procaine towild-type strains alsocausesa pleiotropic decrease inthe expression ofgenesompF,lamB,andphoA.However, procaine hasnoeffect on thesynthesis ofLamB orPhoAprotein intheenvZamberstrains. Thus,although EnvZprotein isrequired forthefull expression ofompFandompC,itapparently isnotnormally involved intheexpression ofotherenvelope protein genes.One interpretation oftheseresults isthattheEnvZprotein canbealtered either by mutation orbyprocaine toa formthatinterferes withtheexpression ofseveral envelope protein genesotherthanompFandompC.Finally, complementation analysis withompRinsertion mutations supports thephysical dataofMizunoet al.(J.Biol. Chem257:13692-13698, 1982) thatsuggest thatenvZiscotranscribed withompRfroma single promoter intheorderompRenvZ.