title: Tautomeric state of alpha-sarcin histidines. Ndelta tautomers are a common feature in the active site of extracellular microbial ribonucleases.
abstract: Extracellular fungal RNases, including ribotoxins such as alpha-sarcin, constitute a family of structurally related proteins represented by RNase T1. The tautomeric preferences of the alpha-sarcin imidazole side chains have been determined by nuclear magnetic resonance and electrostatic calculations. Histidine residues at the active site, H50 and H137, adopt the Ndelta tautomer, which is less common in short peptides, as has been found for RNase T1. Comparison with tautomers predicted from crystal structures of other ribonucleases suggests that two active site histidine residues with the Ndelta tautomer are a conserved feature of microbial ribonucleases and that this is related to their ribonucleolytic function.
authors.affiliation: Departamento de Espectroscopía y Estructura Molecular, Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain.
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Pérez-Cañadilllas
authors.forename: Ma Flor
authors.initials: MF
authors.lastname: García-Mayoral
authors.forename: Douglas V
authors.initials: DV
authors.lastname: Laurents
authors.forename: Alvaro
authors.initials: A
authors.lastname: Martínez del Pozo
authors.forename: José G
authors.initials: JG
authors.lastname: Gavilanes
authors.forename: Manuel
authors.initials: M
authors.lastname: Rico
authors.forename: Marta
authors.initials: M
authors.lastname: Bruix
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D004722:Endoribonucleases / Q000737:chemistry* / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism; D006639:Histidine / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011487:Protein Conformation; D012260:Ribonucleases / Q000737:chemistry / Q000378:metabolism; D055672:Static Electricity
chemical_list: D001426:Bacterial Proteins; D005656:Fungal Proteins; D007093:Imidazoles; C014801:alpha-sarcin; D006639:Histidine; D004722:Endoribonucleases; D012260:Ribonucleases