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The unusual catalytic triad of poliovirus protease 3C.
Biochemistry
January 2003
Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 7, H-1518 Budapest, Hungary.
Picornaviruses are small pathogen RNA viruses, like poliovirus, hepatitis A virus, rhinovirus, and others. They produce a large polyprotein, which is cleaved by virally encoded cysteine peptidases, picornains 2A and 3C. Picornain 3C represents an intermediate between the serine peptidase chymotrypsin and the cysteine peptidase papain.
View Article and Find Full Text PDFThiolate-imidazolium ion pair is not an obligatory catalytic entity of cysteine peptidases: the active site of picornain 3C.
Biochemistry
September 2001
Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, P. O. Box 7, H-1518 Budapest, Hungary.
Cysteine peptidases are thought to attack the substrate by a thiolate-imidazolium ion-pair, as demonstrated with the most extensively studied papain. Picornavirus proteinases (picornains), a different family of cysteine peptidases, are structurally related to the trypsin family of serine peptidases, whose catalytically competent histidine operates as a general base catalyst. Measuring the absorbance change upon alkylation of picornains at 250 nm, where the nondissociated thiol group has a negligible absorbance relative to the ionized form, one can test the ionization state of the catalytic cysteine.
View Article and Find Full Text PDFEvolutionary lines of cysteine peptidases.
Biol Chem
May 2001
MRC Molecular Enzymology Laboratory, The Babraham Institute, Cambridgeshire, UK.
The proteolytic enzymes that depend upon a cysteine residue for activity have come from at least seven different evolutionary origins, each of which has produced a group of cysteine peptidases with distinctive structures and properties. We show here that the characteristic molecular topologies of the peptidases in each evolutionary line can be seen not only in their three-dimensional structures, but commonly also in the two-dimensional structures. Clan CA contains the families of papain (C1), calpain (C2), streptopain (C10) and the ubiquitin-specific peptidases (C12, C19), as well as many families of viral cysteine endopeptidases.
View Article and Find Full Text PDFCharacterization of the active site thiol group of rhinovirus 2A proteinase.
FEBS Lett
September 2000
Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, PO Box 7, Budapest H-1518, Hungary.
Picornains 2A are cysteine proteases of picornaviruses, a virus family containing several human and animal pathogens. The pH dependencies of the alkylations of picornain 2A of rhinovirus type 2 with iodoacetamide and iodoacetate show two reactive thiol forms, namely the free thiolate ion at high pH and an imidazole assisted thiol group at low pH. Kinetic deuterium isotope effects do not support general base catalysis by the imidazole group, but rather the existence of a catalytically competent thiolate-imidazolium ion-pair.
View Article and Find Full Text PDFPicornains 2A and 3C.
Methods Enzymol
March 1995
Department of Biochemistry, Medical Faculty, University of Vienna, Austria.
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