A new Escherichia coli gene, fdrA, identified by suppression analysis of dominant negative FtsH mutations.

An Escherichia coli membrane protein, FtsH, has been implicated in several cellular processes, including integration of membrane proteins, translocation of secreted proteins, and degradation of some unstable proteins. However, how it takes part in such diverse cellular events is largely unknown. We previously isolated dominant negative ftsH mutations and proposed that FtsH functions in association with some other cellular factor(s). To test this proposal we isolated multicopy suppressors of dominant negative ftsH mutations. One of the multicopy suppressor clones contained an N-terminally truncated version of a new gene that was designated fdrA. The FdrA fragment suppressed both of the phenotypes--increased abnormal translocation of a normally cytoplasmic domain of a model membrane protein and retardation of protein export--caused by dominant negative FtsH proteins. The intact fdrA gene (11.9 min on the chromosome) directed the synthesis of a 60 kDa protein in vitro.