Amputation of a C-terminal helix of the γ subunit increases ATP-hydrolysis activity of cyanobacterial F1 ATP synthase

Autor: Ei-Ichiro Sunamura, Toru Hisabori, Kumiko Kondo, Yuki Fukaya, Yu Takeyama, Atsuko Isu, Yuka Madoka
Rok vydání: 2018
Předmět:
Zdroj: Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1859:319-325
ISSN: 0005-2728
DOI: 10.1016/j.bbabio.2018.02.004
Popis: F1 is a soluble part of FoF1-ATP synthase and performs a catalytic process of ATP hydrolysis and synthesis. The γ subunit, which is the rotary shaft of F1 motor, is composed of N-terminal and C-terminal helices domains, and a protruding Rossman-fold domain located between the two major helices parts. The N-terminal and C-terminal helices domains of γ assemble into an antiparallel coiled-coil structure, and are almost embedded into the stator ring composed of α3β3 hexamer of the F1 molecule. Cyanobacterial and chloroplast γ subunits harbor an inserted sequence of 30 or 39 amino acids length within the Rossman-fold domain in comparison with bacterial or mitochondrial γ. To understand the structure-function relationship of the γ subunit, we prepared a mutant F1-ATP synthase of a thermophilic cyanobacterium, Thermosynechococcus elongatus BP-1, in which the γ subunit is split into N-terminal α-helix along with the inserted sequence and the remaining C-terminal part. The obtained mutant showed higher ATP-hydrolysis activities than those containing the wild-type γ. Contrary to our expectation, the complexes containing the split γ subunits were mostly devoid of the C-terminal helix. We further investigated the effect of post-assembly cleavage of the γ subunit. We demonstrate that insertion of the nick between two helices of the γ subunit imparts resistance to ADP inhibition, and the C-terminal α-helix is dispensable for ATP-hydrolysis activity and plays a crucial role in the assembly of F1-ATP synthase.
Databáze: OpenAIRE
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