2z1h
Crystal structure of E.coli RNase HI surface charged mutant(Q4R/T92K/Q105K/Q113R/Q115K/N143K/T145K)
Structural highlights
FunctionRNH_ECOLI Endonuclease that specifically degrades the RNA of RNA-DNA hybrids. RNase H participates in DNA replication; it helps to specify the origin of genomic replication by suppressing initiation at origins other than the oriC locus; along with the 5'-3' exonuclease of pol1, it removes RNA primers from the Okazaki fragments of lagging strand synthesis; and it defines the origin of replication for ColE1-type plasmids by specific cleavage of an RNA preprimer.[HAMAP-Rule:MF_00042] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedUsing the information from the genome projects, recent comparative studies of thermostable proteins have revealed a certain trend of amino acid composition in which polar residues are scarce and charged residues are rich on the protein surface. To clarify experimentally the effect of the amino acid composition of surface residues on the thermostability of Escherichia coli Ribonuclease HI (RNase HI), we constructed six variants in which five to eleven polar residues were replaced by charged residues (5C, 7Ca, 7Cb, 9Ca, 9Cb and 11C). The thermal denaturation experiments indicated that all of the variant proteins are 3.2-10.1 degrees C in Tm less stable than the wild proteins. The crystal structures of resultant protein variants 7Ca, 7Cb, 9Ca and 11C closely resemble that of E. coli RNase HI in their global fold, and several different hydrogen bonding and ion-pair interactions are formed by the mutations. Comparison of the crystal structures of these variant proteins with that of E. coli RNase HI reveals that thermal destabilization is apparently related to electrostatic repulsion of the charged residues with neighbours. This result suggests that charged residues of natural thermostable proteins are strictly posted on the surface with optimal interactions and without repulsive interactions. Protein thermostabilization requires a fine-tuned placement of surface-charged residues.,You DJ, Fukuchi S, Nishikawa K, Koga Y, Takano K, Kanaya S J Biochem. 2007 Oct;142(4):507-16. Epub 2007 Aug 30. PMID:17761696[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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