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An ancestral nuclear protein assembly: Crystal structure of the Methanopyrus kandleri histone
Author(s) -
Fahrner Richard L.,
Cascio Duilio,
Lake James A.,
Slesarev Alexei
Publication year - 2001
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.10901
Subject(s) - nucleosome , biology , histone h4 , histone octamer , histone h1 , histone , histone h2a , histone code , biochemistry , genetics , dna
Eukaryotic histone proteins condense DNA into compact structures called nucleosomes. Nucleosomes were viewed as a distinguishing feature of eukaryotes prior to ideication of histone orthologs in methanogens. Although evolutionarily distinct from methanogens, the methane‐producing hyperthermophile Methanopyrus kandleri produces a novel, 154‐residue histone (HMk). Amino acid sequence comparisons show that HMk differs from both methanogenic and eukaryotic histones, in that it contains two histone‐fold ms within a single chain. The two HMk histone‐fold ms, N and C terminal, are 28% identical in amino acid sequence to each other and ∼21% identical in amino acid sequence to other histone proteins. Here we present the 1.37‐Å‐resolution crystal structure of HMk and report that the HMk monomer structure is homologous to the eukaryotic histone heterodimers. In the crystal, HMk forms a dimer homologous to [H3–H4] 2 in the eukaryotic nucleosome. Based on the spatial similarities to structural ms found in the eukaryotic nucleosome that are important for DNA‐binding, we infer that the Methanopyrus histone binds DNA in a manner similar to the eukaryotic histone tetramer [H3–H4] 2 .