title: Structure of human endonuclease V as an inosine-specific ribonuclease.
abstract: The 6-aminopurine ring of adenosine (A) can be deaminated to form the 6-oxopurine of inosine (I). Endonuclease Vs (EndoVs) are inosine-specific nucleases that cleave at the second phosphodiester bond 3' to inosine. EndoV proteins are highly conserved in all domains of life, but the bacterial and human enzymes seem to display distinct substrate preferences. While the bacterial enzymes exhibit high cleavage efficiency on various nucleic acid substrates, human EndoV (hEndoV) is most active towards ssRNA but is much less active towards other substrates. However, the structural basis of substrate recognition by hEndoV is not well understood. In this study, the 2.3 Å resolution crystal structure of hEndoV was determined and its unusual RNA-cleaving properties were investigated. The enzyme preserves the general `RNase H-like' structure, especially in the wedge motif, the metal-binding site and the hypoxanthine-binding pocket. hEndoV also features several extra insertions and a characteristic four-cysteine motif, in which Cys227 and Cys228, two cysteines that are highly conserved in higher eukaryotes, play important roles in catalysis. The structure presented here helps in understanding the substrate preference of hEndoV catalysis.
authors.affiliation: Key Laboratory of Gene Engineering of the Ministry of Education, State Key Laboratory for Biocontrol, School of Life Sciences, The Sun Yat-Sen University, Guangzhou 510275, People's Republic of China.
authors.forename: Zhemin
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Gene Engineering of the Ministry of Education, State Key Laboratory for Biocontrol, School of Life Sciences, The Sun Yat-Sen University, Guangzhou 510275, People's Republic of China.
authors.forename: Zhitai
authors.initials: Z
authors.lastname: Hao
authors.affiliation: Centre for Cellular and Structural Biology, The Sun Yat-Sen University, 132 East Circle Road, University City, Guangzhou 510006, People's Republic of China.
authors.forename: Zhong
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Centre for Cellular and Structural Biology, The Sun Yat-Sen University, 132 East Circle Road, University City, Guangzhou 510006, People's Republic of China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
authors.affiliation: Key Laboratory of Gene Engineering of the Ministry of Education, State Key Laboratory for Biocontrol, School of Life Sciences, The Sun Yat-Sen University, Guangzhou 510275, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Xie
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D043224:Deoxyribonuclease (Pyrimidine Dimer) / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007288:Inosine / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D012260:Ribonucleases / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D007288:Inosine; D012260:Ribonucleases; D043224:Deoxyribonuclease (Pyrimidine Dimer)
keywords: EndoV; RNase H-like motif; deamination; hypoxanthine; ribonuclease