The three-dimensional structure and X-ray sequence reveal that trichomaglin is a novel S-like ribonuclease.
Trichomaglin is a protein isolated from root tuber of the plant Maganlin (Trichosanthes Lepiniate, Cucurbitaceae). The crystal structure of trichomaglin has been determined by multiple-isomorphous replacement and refined at 2.2 A resolution. The X-ray sequence was established, based on electron density combined with the experimentally determined N-terminal sequence, and the sequence information derived from mass spectroscopic analysis. X-ray sequence-based homolog search and the three-dimensional structure reveal that trichomaglin is a novel S-like RNase, which was confirmed by biological assay. Trichomaglin molecule contains an additional beta sheet in the HV(b) region, compared with the known plant RNase structures. Fourteen cystein residues form seven disulfide bridges, more than those in the other known structures of S- and S-like RNases. His43 and His105 are expected to be the catalytic acid and base, respectively. Four hydrosulfate ions are bound in the active site pocket, three of them mimicking the substrate binding sites.
Gan
Jian-Hua
JH
State Key Laboratory of Bio-organic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China.
Yu
Lu
L
Wu
Jian
J
Xu
Hong
H
Choudhary
Joyti S
JS
Blackstock
Walter P
WP
Liu
Wang-Yi
WY
Xia
Zong-Xiang
ZX
D000595:Amino Acid Sequence; D001665:Binding Sites; D002384:Catalysis; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry; D004220:Disulfides; D004583:Electrons; D006639:Histidine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007477:Ions; D013058:Mass Spectrometry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012260:Ribonucleases / Q000737:chemistry*; D054789:Ribosome Inactivating Proteins, Type 1; D017386:Sequence Homology, Amino Acid; D012984:Software
D004220:Disulfides; D007477:Ions; D010940:Plant Proteins; D054789:Ribosome Inactivating Proteins, Type 1; D006639:Histidine; D012260:Ribonucleases; D009699:N-Glycosyl Hydrolases; C119173:trichomaglin; D003545:Cysteine