ComP, a pilin-like protein essential for natural competence in Acinetobacter sp strain BD413: Regulation, modification, and cellular localization

We recently identified a pilin-like competence factor, ComP, which is essen tial for natural transformation of the gram-negative soil bacterium Acineto bacter sp, strain BD413, Here we demonstrate that transcription and synthes is of the pilin-like competence factor ComP are maximal in the late station ary growth phase, whereas competence is induced immediately after inoculati on of a stationary-phase culture into fresh medium. Western blot analyses r evealed three forms of ComP, one with an apparent molecular mass of 15 kDa, which correlates with the molecular mass deduced from the DNA sequence, on e 20-kDa form, which was found to be glycosylated, and one 23-kDa form. The glycosylation of ComP was not required for its function in DNA binding and uptake. The 20-kDa form was present in the cytoplasmic membrane, the perip lasm, and the outer membrane, whereas the 23-kDa form was located in the ou ter membrane and might be due to a further modification. Immunological data suggest that ComP is not a subunit of the pilus structures, Possible funct ions of ComP in the DNA transformation machinery of Acinebacter sp. strain BD413 are discussed.