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Interaction of a small heat shock protein with light‐harvesting cyanobacterial phycocyanins under stress conditions
Author(s) -
Nakamoto Hitoshi,
Honma Daisuke
Publication year - 2006
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2006.04.047
Subject(s) - phycobilisome , phycobiliprotein , lysozyme , allophycocyanin , phycocyanin , heat shock protein , biophysics , chemistry , cyanobacteria , monomer , biochemistry , denaturation (fissile materials) , biology , nuclear chemistry , bacteria , genetics , organic chemistry , gene , polymer
Phycobiliproteins such as phycocyanins are the most abundant proteins found in cyanobacteria which are assembled to form the phycobilisome. Here, we showed that a small heat shock protein, HspA, interacts directly with phycocyanins from the cyanobacterium Synechococcus sp. strain PCC 7942 in vitro and suppresses inactivation of their light‐harvesting functions due to heat denaturation in the presence of hydrogen peroxide. Under the denaturing conditions, phycobilisomes were de‐assembled to lighter complexes and then aggregated. HspA associated with phycocyanins in the dissociated complexes, and suppressed the aggregation. The specific interaction between a small heat shock protein and phycocyanins was further supported by the fact that HspA and α‐crystallin protected isolated phycocyanins from denaturation, while HtpG and lysozyme did not. The maximum protection was observed at a molar ratio of four HspA monomer per one phycocyanin (αβ) monomer.