Summary The product of the
dye gene of
Escherichia coli, mapping at 99–100 min, is required for expression of the sex factor F, and also appears to be involved in the regulation of envelope proteins. Mutation of
dye thus results in loss of expression of the F-factor (Fex
–, i.e. male sterility, and dye sensitivity (Dye
s). We have isolated a plasmid, pRB38, in which a 6 kb
SalI fragment carrying the
dye
+ gene was cloned into the plasmid pACYC184. This 6 kb
SalI fragment also carries two nearby markers,
chlG, involved in the synthesis of the molybdenum cofactor, and
phoM, required for constitutive expression of alkaline phosphatase.Some of the polypeptides synthesised by pRB38 were identified using the maxi-cell procedure. The product of the
dye gene was found to be a polypeptide of M
r=29,000. Thus derivatives of pRB38 in which the transposon was inserted into
dye, resulting in a Dye
S Fex
– phenotype when these plasmids were in a
dye strain, failed to produce this polypeptide and in some cases produced a truncated product. Such insertions also resulted in a Chl
r and Pho
– phenotype when the plasmid was in a (
dye-chlG-phoM) phoR strain, although complementation tests suggested that the
phoM
+ and
chlG
+ genes were still intact. Insertions of into the promoter distal end of
dye did not result in a Dye
S Fex
– phenotype, although a truncated Dye protein was synthesised, and a Chl
r Pho
– phenotype was produced.It has been suggested (Gaffney et al. 1983) that the
dye (=
sfrA) gene product is necessary for F-factor expression because it is required for translocation of the F-factor TraJ protein to the outer membrane. Our results suggest that the Dye protein is also required for expression of the molybdenum cofactor and of alkaline phosphatase, and could perhaps be involved in the translocation of these proteins to the membrane.
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