Abstract
The basis for transcriptional fidelity by RNA polymerase is not understood, but the 'trigger loop', a conserved structural element that is rearranged in the presence of correct substrate nucleotides, is thought to be critical. A study just published in BMC Biology sheds new light on the ways in which the trigger loop may promote selection of correct nucleotide triphosphate substrates.See research article http://www.biomedcentral.com/1741-7007/8/54
Highlights
The basis for transcriptional fidelity by RNA polymerase is not understood, but the ‘trigger loop’, a conserved structural element that is rearranged in the presence of correct substrate nucleotides, is thought to be critical
The understanding of the enzymatic activity of multisubunit RNA polymerases (RNAPs) has reached a level of detail where the contributions of individual amino acid residues can be studied within an emerging structural framework, and this framework has provided the context for a kinetic analysis of mutant Thermus aquaticus RNAPs published in BMC Biology by Yuzenkova et al [2], who show how substrates can be screened at several steps in the synthetic process for their appropriateness before incor poration into a growing RNA chain, and make detailed suggestions on the structural basis for the discrimination
The central role of the trigger loop The evidence for the role of rearrangement of the active site comes from structural studies on highly structurally related RNAPs from many organisms [3], which have shown that the trigger loop can adopt multiple confor mations, and studies on Pol II of Sacharomyces cerevisiae [5] and RNAP of Thermus thermophilus [6] in which it undergoes a structural reorganization that is dependent on the binding of a matched substrate
Summary
The basis for transcriptional fidelity by RNA polymerase is not understood, but the ‘trigger loop’, a conserved structural element that is rearranged in the presence of correct substrate nucleotides, is thought to be critical. The understanding of the enzymatic activity of multisubunit RNAPs has reached a level of detail where the contributions of individual amino acid residues can be studied within an emerging structural framework, and this framework has provided the context for a kinetic analysis of mutant Thermus aquaticus RNAPs published in BMC Biology by Yuzenkova et al [2], who show how substrates can be screened at several steps in the synthetic process for their appropriateness before incor poration into a growing RNA chain, and make detailed suggestions on the structural basis for the discrimination.
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