A NEW ESCHERICHIA-COLI GENE, FDRA, IDENTIFIED BY SUPPRESSION ANALYSISOF DOMINANT-NEGATIVE FTSH MUTATIONS

An Escherichia coli membrane protein, FtsH, has been implicated in sev eral cellular processes, including integration of membrane proteins, t ranslocation of secreted proteins, and degradation of some unstable pr oteins. However, how it takes part in such diverse cellular events is largely unknown. We previously isolated dominant negative ftsH mutatio ns and proposed that FtsH functions in association with some other cel lular factor(s). To test this proposal we isolated multicopy suppresso rs of dominant negative ftsH mutations. One of the multicopy suppresso r clones contained an N-terminally truncated version of a new gene tha t was designated fdrA. The FdrA fragment suppressed both of the phenot ypes - increased abnormal translocation of a normally cytoplasmic doma in of a model membrane protein and retardation of protein export - cau sed by dominant negative FtsH proteins. The intact fdrA gene (11.9 min on the chromosome) directed the synthesis of a 60 kDa protein in vitr o.