How the CCA-Adding Enzyme Selects Adenine over Cytosine at Position 76 of tRNA

Journal Article · Sat Dec 31 04:00:00 EST 2011 · Science (Washington, D.C.)

OSTI ID:1041976

Pan, B; Xiong, Y; Steitz, T

CCA-adding enzymes [ATP(CTP):tRNA nucleotidyltransferases] add CCA onto the 3' end of transfer RNA (tRNA) precursors without using a nucleic acid template. Although the mechanism by which cytosine (C) is selected at position 75 of tRNA has been established, the mechanism by which adenine (A) is selected at position 76 remains elusive. Here, we report five cocrystal structures of the enzyme complexed with both a tRNA mimic and nucleoside triphosphates under catalytically active conditions. These structures suggest that adenosine 5'-monophosphate is incorporated onto the A76 position of the tRNA via a carboxylate-assisted, one-metal-ion mechanism with aspartate 110 functioning as a general base. The discrimination against incorporation of cytidine 5'-triphosphate (CTP) at position 76 arises from improper placement of the {alpha} phosphate of the incoming CTP, which results from the interaction of C with arginine 224 and prevents the nucleophilic attack by the 3' hydroxyl group of cytidine75.

• Research Organization: BROOKHAVEN NATIONAL LABORATORY (BNL)
• Sponsoring Organization: USDOE SC OFFICE OF SCIENCE (SC)
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1041976
• Report Number(s): BNL--97654-2012-JA
• Journal Information: Science (Washington, D.C.), Journal Name: Science (Washington, D.C.) Journal Issue: 6006 Vol. 330; ISSN SCIEAS; ISSN 0036-8075
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
60 APPLIED LIFE SCIENCES
ADENINES
ADENOSINE
ARGININE
CYTIDINE
CYTOSINE
ENZYMES
NUCLEIC ACIDS
NUCLEOSIDES
NUCLEOTIDYLTRANSFERASES
PHOSPHATES
TRANSFER RNA