Characterization of StiP, a starvation‐induced cysteine protease from Acinetobacter baylyi (933.4)

Abstract

We have investigated the gene ACIAD 1960 from Acinetobacter baylyi. A. baylyi is a soil bacterium that is of interest due to its ability to utilize a diverse set of nutrients as a source of carbon and nitrogen, and to its high level of competence with regards to natural transformation. Medically, it is becoming of interest as a potential source of hospital‐acquired infections. Previous work has shown that gene ACIAD1960 is expressed during long‐term stationary phase. We identified that the purified protein expressed by ACIAD 1960 encodes a cysteine protease activity. We named the cysteine protease “StiP” to reflect that it is a long‐term stationary phase induced protease. We present data from a deletion‐insertion mutation which demonstrates that lack of the protein causes alteration of normal cell morphology, smaller twitching zone size, and hypersensitivity to the oxyanion tellurite. The mutant may also have a small growth defect. We show that the presence of divalent metal ions differentially affect its activity. The presence of Ca2+, Mg2+ and Mn2+ all increase activity, with Mn2+ showing the greatest effect. The presence of Zn2+ significantly decreases activity. Additionally, we show that StiP activity decreases in the presence of reducing agents, suggesting that a disulfide bond maycontribute to its overall conformational stability and function. Grant Funding Source: Supported by Colorado College Natural Sciences Executive Committee grants to M.A.D., K.M.L., and C.