A signal sequence is not required for protein export in prlA mutants of Escherichia coli.
AUTOR(ES)
Derman, A I
RESUMO
The prlA/secY gene, which codes for an integral membrane protein component of the Escherichia coli protein export machinery, is the locus of the strongest suppressors of signal sequence mutations. We demonstrate that two exported proteins of E.coli, maltose-binding protein and alkaline phosphatase, each lacking its entire signal sequence, are exported to the periplasm in several prlA mutants. The export efficiency can be substantial; in a strain carrying the prlA4 allele, 30% of signal-sequenceless alkaline phosphatase is exported to the periplasm. Other components of the E.coli export machinery, including SecA, are required for this export. SecB is required for the export of signal-sequenceless alkaline phosphatase even though the normal export of alkaline phosphatase does not require this chaperonin. Our findings indicate that signal sequences confer speed and efficiency upon the export process, but that they are not always essential for export. Entry into the export pathway may involve components that so overlap in function that the absence of a signal sequence can be compensated for, or there may exist one or more means of entry that do not require signal sequences at all.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=413286Documentos Relacionados
- prlA suppression of defective export of maltose-binding protein in secB mutants of Escherichia coli.
- PrlA is important for the translocation of exported proteins across the cytoplasmic membrane of Escherichia coli.
- Two cellular components, PrlA and SecB, that recognize different sequence determinants are required for efficient protein export.
- Novel prlA alleles defective in supporting staphylokinase processing in Escherichia coli.
- PrlA and PrlG suppressors reduce the requirement for signal sequence recognition.
