期刊
JOURNAL OF MOLECULAR BIOLOGY
卷 300, 期 4, 页码 935-950出版社
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1006/jmbi.2000.3909
关键词
methanogenesis; methanopterin; folate; X-ray structure; TIM-barrel
Coenzyme F-420-dependent methylenetetrahydromethanopterin reductase (Mer) is an enzyme of the Cl metabolism in methanogenic and sulfate reducing archaea. It is composed of identical 35-40 kDa subunits and lacks a prosthetic group. The crystal structure of Mer from Methanopyrus kandleri (kMer) revealed in one crystal form a dimeric and in another a tetrameric oligomerisation state and that from Methanobacterium thermoautotrophicum (tMer) a dimeric state. Each monomer is primarily composed of a TIM-barrel fold enlarged by three insertion regions. Insertion regions 1 and 2 contribute to intersubunit interactions. Insertion regions 2 and 3 together with the C-terminal end of the TIM-barrel core form a cleft where the binding sites of coenzyme F-420 and methylene-tetrahydromethanopterin are postulated. Close to the coenzyme F-420-binding site lies a rarely observed non-prolyl cis-peptide bond. It is surprising that Mer is structurally most similar to a bacterial FMN-dependent luciferase which contains a non-prolyl cis-peptide bond at the equivalent position. The structure of Mer is also related to that of NADP-dependent FAD-harbouring methylenetetrahydrofolate reductase (MetF). However, Mer and MetF do not show sequence similarities although they bind related substrates and catalyze an analogous reaction. (C) 2000 Academic Press.
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