Functions of a hemolysin-like protein in the cyanobacterium Synechocystis sp. PCC 6803

概要

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A glucose-tolerant strain of the cyanobacterium Synechocystis sp. PCC 6803, generally referred to as wild type, produces a hemolysin-like protein (HLP) located on the cell surface. To analyze the function of HLP, we constructed a mutant in which the hlp gene was disrupted. The growth rate of the mutant was reduced when the cells were stressed by treatment with CuSO4, CdCl2, ZnCl2, ampicillin, kanamycin, or sorbitol in liquid medium, suggesting that HLP may increase cellular resistance to the inhibitory effects of these compounds. Uptake assays with 109Cd2+ using the silicone–oil layer centrifugation technique revealed that both wild type and mutant cells were labeled with 109Cd2+ within 1 min. Although the total radioactivity was much higher in the wild-type cells, 109Cd2+ incorporation was clearly much higher in the mutant cells after adsorbed 109Cd2+ was removed from the cell surface by washing with EDTA. These findings suggest that HLP functions as a barrier against the adsorption of toxic compounds.