Dual mechanisms whereby a broken RNA end assists the catalysis of its repair by T4 RNA ligase 2 Journal Article

  

Authors:	Nandakumar, J.; Shuman, S.
Article Title:	Dual mechanisms whereby a broken RNA end assists the catalysis of its repair by T4 RNA ligase 2
Abstract:	T4 RNA ligase 2 (Rnl2) efficiently seals 3′-OH/5′-PO 4 RNA nicks via three nucleotidyl transfer steps. Here we show that the terminal 3′-OH at the nick accelerates the second step of the ligase pathway (adenylylation of the 5′-PO4 strand) by a factor of 1000, even though the 3′-OH is not chemically transformed during the reaction. Also, the terminal 2′-OH at the nick accelerates the third step (attack of the 3′-OH on the 5′-adenylated strand to form a phosphodiester) by a factor of 25-35, even though the 2′-OH is not chemically reactive. His-37 of Rnl2 is uniquely required for step 3, providing a ∼102 rate acceleration. Biochemical epistasis experiments show that His-37 and the RNA 2′-OH act independently. We conclude that the broken RNA end promotes catalysis of its own repair by Rnl2 via two mechanisms, one of which (enhancement of step 3 by the 2′-OH) is specific to RNA ligation. Substrate-assisted catalysis provides a potential biochemical checkpoint during nucleic acid repair. © 2005 by The American Society for Biochemistry and Molecular Biology, Inc.
Keywords:	controlled study; unclassified drug; mutation; nonhuman; carboxy terminal sequence; rna; amino terminal sequence; kinetics; nucleic acids; catalysis; rna processing; enzymes; lysine; rna ligase (atp); histidine; rna, viral; esters; chemical bond; viral proteins; ligase; adenylation; phosphodiester; adenylylation; rna ligase; genetic epistasis; epistasis, genetic; biocatalysts; substrate-assisted catalysis; rna ligase 2; phocidae
Journal Title:	Journal of Biological Chemistry
Volume:	280
Issue:	25
ISSN:	0021-9258
Publisher:	American Society for Biochemistry and Molecular Biology
Date Published:	2005-06-24
Start Page:	23484
End Page:	23489
Language:	English
DOI:	10.1074/jbc.M500831200
PUBMED:	15851476
PROVIDER:	scopus
DOI/URL:	http://www.scopus.com/inward/record.url?eid=2-s2.0-21244444714&partnerID=40&md5=4ce705b006afc7ba3f3cc088ce337bb7
Notes:	--- - "Cited By (since 1996): 10" - "Export Date: 24 October 2012" - "CODEN: JBCHA" - "Source: Scopus"

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