Abstract
We showed that the inactivation of the htpG gene from the cyanobacterium Synechococcus sp. PCC 7942 causes loss in both basal and acquired thermo-tolerances, indicating an indispensable role of the HtpG protein for the survival under high-temperature stress.
We observed the reduction of phycocyanin content in the htpG mutant grown under normal conditions. The phycobilisome purified from the mutant by sucrose density gradient ultra-centrifugation is lighter than that from the wild type. Phycobilisomes are composed of phycobiliproteins and linker polypeptides. In contrast to phycobiliproteins, linker polypeptides were prone to aggregation when dissociated from the phycobilisome complex. We found that the level of the 30-kDa linker polypeptide is reduced in the mutant's phycobilisome and that the purified HtpG can prevent the in vitro aggregation of the linker polypeptides at normal and high temperatures. Studies on an interaction between HtpG and a linker polypeptide are in progress.
