Biomaterial Database

Histidine tRNA guanylyltransferase from Saccharomyces cerevisiae. II. Catalytic mechanism. 1991

D Jahn, and S Pande

Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511.

Yeast histidine tRNA guanylyltransferase (TGT) catalyzes in the presence of ATP the addition of GTP to the 5' end of eukaryotic cytoplasmic tRNAHis species. A study of the enzyme mechanism with purified protein showed that during the first step ATP is cleaved to AMP and PPi creating adenylylated TGT. In a second step the activated enzyme forms a stable complex with its cognate tRNA substrate. The 5'-phosphate of the tRNA is adenylylated by nucleotide transfer from the adenylylated guanylyltransferase to form A(5')pp(5')N at the 5'-end of the tRNA. Finally, the 3'-hydroxyl of GTP adds to the activated 5' terminus of the tRNA with the release of AMP. This mechanism of tRNAHis guanylyltransferase is very similar to that of RNA ligases. dATP can substitute for ATP in this reaction. Since among several guanosine compounds active in this reaction GTP is most efficiently added we believe that it is the natural substrate of TGT.

UI	MeSH Term	Description	Entries
D009713	Nucleotidyltransferases	A class of enzymes that transfers nucleotidyl residues. EC 2.7.7.	Nucleotidyltransferase
D002384	Catalysis	The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction.	Catalyses
D004591	Electrophoresis, Polyacrylamide Gel	Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.	Polyacrylamide Gel Electrophoresis,SDS-PAGE,Sodium Dodecyl Sulfate-PAGE,Gel Electrophoresis, Polyacrylamide,SDS PAGE,Sodium Dodecyl Sulfate PAGE,Sodium Dodecyl Sulfate-PAGEs
D004789	Enzyme Activation	Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme.	Activation, Enzyme,Activations, Enzyme,Enzyme Activations
D006160	Guanosine Triphosphate	Guanosine 5'-(tetrahydrogen triphosphate). A guanine nucleotide containing three phosphate groups esterified to the sugar moiety.	GTP,Triphosphate, Guanosine
D000225	Adenine	A purine base and a fundamental unit of ADENINE NUCLEOTIDES.	Vitamin B 4,4, Vitamin B,B 4, Vitamin
D000255	Adenosine Triphosphate	An adenine nucleotide containing three phosphate groups esterified to the sugar moiety. In addition to its crucial roles in metabolism adenosine triphosphate is a neurotransmitter.	ATP,Adenosine Triphosphate, Calcium Salt,Adenosine Triphosphate, Chromium Salt,Adenosine Triphosphate, Magnesium Salt,Adenosine Triphosphate, Manganese Salt,Adenylpyrophosphate,CaATP,CrATP,Manganese Adenosine Triphosphate,MgATP,MnATP,ATP-MgCl2,Adenosine Triphosphate, Chromium Ammonium Salt,Adenosine Triphosphate, Magnesium Chloride,Atriphos,Chromium Adenosine Triphosphate,Cr(H2O)4 ATP,Magnesium Adenosine Triphosphate,Striadyne,ATP MgCl2
D012354	RNA, Transfer, His	A transfer RNA which is specific for carrying histidine to sites on the ribosomes in preparation for protein synthesis.	Histidine-Specific tRNA,Transfer RNA, His,tRNAHis,tRNA(His),His Transfer RNA,Histidine Specific tRNA,RNA, His Transfer,tRNA, Histidine-Specific
D012441	Saccharomyces cerevisiae	A species of the genus SACCHAROMYCES, family Saccharomycetaceae, order Saccharomycetales, known as "baker's" or "brewer's" yeast. The dried form is used as a dietary supplement.	Baker's Yeast,Brewer's Yeast,Candida robusta,S. cerevisiae,Saccharomyces capensis,Saccharomyces italicus,Saccharomyces oviformis,Saccharomyces uvarum var. melibiosus,Yeast, Baker's,Yeast, Brewer's,Baker Yeast,S cerevisiae,Baker's Yeasts,Yeast, Baker