Similarities in the induction of synthesis of a cell-surface polypeptide in Arthrobacter sp. by near-UV irradiation and photodynamic conditions

Molecular cloning of a light-inducible gene (lipA) encoding a novel pilin from Arthrobacter photogonimos

Development of pili on cells of Arthrobacter photogonimos is induced by photo-oxidative conditions. The nucleotide sequence was determined of a light-inducible gene (lipA) that encodes the precursor of a light-inducible pilin (designated LIP), a polypeptide of 212 amino acids. The N-terminal leader peptide includes a typical signal sequence with a consensus cleavage site for signal peptidase 1 after residue 28, which should generate N-terminal arginine. However, the next amino acid, alanine, is the N-terminal residue of the mature protein. The abundance of charged amino acids (27% of total), a calculated pI of 9.98, and recovery of mostly monomers when cells were washed with 1 M NaCl suggest that electrostatic interactions play a dominant role in association of LIP, a novel mechanism for assembly of pili.

Induction of a light-inducible gene in Arthrobacter sp. by exposure of cells to chelating agents and pH 5

Transcription of a light-inducible gene in the prokaryote Arthrobacter sp. is induced in the dark when cells are incubated with chelating agents or in medium at pH 5. However, repletion of metal ions such as Ca2+, Mn2+ or Zn2+ or an increase in pH is required for accumulation of the gene product, an Mr 21,000 polypeptide. But such changes in condition restore repression of the gene, and the decay in the rate of synthesis of the polypeptide follows the same time-course as when photodynamically induced cells are transferred to the dark. These results are consistent with regulation of expression of this gene at transcriptional and posttranscriptional steps by mechanisms that involve metal-protein complexes.