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The E3 ligase AtCHIP ubiquitylates FtsH1, a component of the chloroplast FtsH protease, and affects protein degradation in chloroplasts
Author(s) -
Shen Guoxin,
Adam Zach,
Zhang Hong
Publication year - 2007
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2007.03239.x
Subject(s) - chloroplast , protein subunit , protease , biology , protein degradation , ubiquitin ligase , hsp70 , photosystem ii , biochemistry , light intensity , microbiology and biotechnology , rubisco , proteolysis , in vivo , arabidopsis , cytoplasm , cytosol , dna ligase , ubiquitin , heat shock protein , enzyme , photosynthesis , mutant , genetics , gene , physics , optics
Summary The Arabidopsis E3 ligase AtCHIP was found to interact with FtsH1, a subunit of the chloroplast FtsH protease complex. FtsH1 can be ubiquitylated by AtCHIP in vitro , and the steady‐state level of FtsH1 is reduced in AtCHIP ‐over‐expressing plants under high‐intensity light conditions, suggesting that the ubiquitylation of FtsH1 by AtCHIP might lead to the degradation of FtsH1 in vivo . Furthermore, the steady‐state level of another subunit of the chloroplast FtsH protease complex, FtsH2, is also reduced in AtCHIP ‐over‐expressing plants under high‐intensity light conditions, and FtsH2 interacts physically with AtCHIP in vivo , suggesting the possibility that FtsH2 is also a substrate protein for AtCHIP in plant cells. A substrate of FtsH protease in vivo , the photosystem II reaction center protein D1, is not efficiently removed by FtsH in AtCHIP ‐over‐expressing plants under high‐intensity light conditions, supporting the assumption that FtsH subunits are substrates of AtCHIP in vivo , and that AtCHIP over‐expression may lead to a reduced level of FtsH in chloroplasts. AtCHIP interacts with cytosolic Hsp70 and the precursors of FtsH1 and FtsH2 in the cytoplasm, and Hsp70 also interacts with FtsH1, and these protein–protein interactions appear to be increased under high‐intensity light conditions, suggesting that Hsp70 might be partly responsible for the increased degradation of the substrates of Hsp70, such as FtsH1 and FtsH2, in AtCHIP ‐over‐expressing plants under high‐intensity light conditions. Therefore, AtCHIP, together with Hsp70, may play an important role in protein quality control in chloroplasts.