Abstract
Although eukaryotic Hsp90 has been well known to play important roles in diverse signal transduction pathways, functions of its prokaryotic counterpart HtpG are not clearly understood. In cyanobacteria Synechococcus sp. PCC7942, we reported previously that HtpG protein increased in response to various stress conditions. In addition, htpG null mutant revealed reduced production of phycocyanin and chlorophyll.
Our systematic analysis of protein-protein interactions by using yeast two-hybrid analysis suggested a specific interaction between HtpG and HemE (uroporphyrinogen decarboxyrase). To analyze the role of HtpG in the HemE activity, the cell lysate of htpG overexpressing strain was prepared and the level of coproporphyrin was compared with that of the wild type strain. The results indicated that HtpG negatively regulated the HemE activity. Furthermore, htpG overexpression inhibited the cell growth, suggesting a detrimental effect of HtpG in cyanobacteria.
