Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.26.4 (RNase H)
 2,751 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

N-terminal amino acid sequencing, ion spray mass spectrometry, and cleavage of synthetic peptide substrates were used to identify the N and C termini of the mature Gag and Pol proteins of feline immunodeficiency virus (FIV). The Gag polyprotein encodes matrix (MA), capsid (CA), and nucleocapsid (NC) proteins. The Gag-Pol polyprotein encodes, in addition to the above proteins, protease (PR), reverse transcriptase (RT), dUTPase (DU), and integrase (IN). Secondary cleavage of RT at Trp-595-Tyr-596 of Pol yields a truncated form lacking the C-terminal RNase H domain. The observed and expected molecular masses of the viral proteins were in agreement, with three exceptions. (i) The molecular mass of MA was 14,735 Da, compared with a predicted mass of 14,649 Da, based on a single cleavage at Tyr-135-Pro-136 of Gag. The observed molecular mass is consistent with myristoylation of MA, which was confirmed by metabolic labeling of FIV MA with [3H]myristic acid. (ii) The N terminus of the NC protein is generated via cleavage at Gln-366-Val-367 of Gag, which predicts a mass of 25,523 for CA and 9,101 for the major form of NC. The observed mass of CA was 24,569, consistent with loss of nine C-terminal amino acids by a second cleavage of CA at Leu-357-Leu-358. Synthetic FIV protease accurately cleaved synthetic peptide substrates containing this site. (iii) The actual mass of NC (7,120 Da) was approximately 2 kDa smaller than the mass predicted by synthesis to the stop codon at the end of Gag (9,101 Da). Experiments are in progress to characterize additional cleavage(s) in NC.
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PMID:Identification of proteolytic processing sites within the Gag and Pol polyproteins of feline immunodeficiency virus. 838 14

In HIV-1, development of resistance to AZT (3'-azido-3'-deoxythymidine) is mediated by the acquisition of thymidine analogue resistance mutations (TAMs) (i.e., M41L, D67N, K70R, L210W, T215F/Y, and K219E/Q) in the viral reverse transcriptase (RT). Clinically relevant combinations of TAMs, such as M41L/T215Y or D67N/K70R/T215F/K219Q, enhance the ATP-mediated excision of AZT monophosphate (AZTMP) from the 3' end of the primer, allowing DNA synthesis to continue. Additionally, during HIV-1 maturation, the Gag polyprotein is cleaved to release a mature nucleocapsid protein (NCp7) and two intermediate precursors (NCp9 and NCp15). NC proteins interact with the viral genome and facilitate the reverse transcription process. Using wild-type and TAM-containing RTs, we showed that both NCp9 and NCp15 inhibited ATP-mediated rescue of AZTMP-terminated primers annealed to RNA templates but not DNA templates, while NCp7 had no effect on rescue activity. RNase H inactivation by introducing the active-site mutation E478Q led to the loss of the inhibitory effect shown by NCp9. NCp15 had a stimulatory effect on the RT's RNase H activity not observed with NCp7 and NCp9. However, analysis of RNase H cleavage patterns revealed that in the presence of NCp9, RNA/DNA complexes containing duplexes of 12 bp had reduced stability in comparison with those obtained in the absence of NC or with NCp7 or NCp15. These effects are expected to have a strong influence on the inhibitory action of NCp9 and NCp15 by affecting the efficiency of RNA-dependent DNA polymerization after unblocking DNA primers terminated with AZTMP and other nucleotide analogues.
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PMID:Nucleocapsid Protein Precursors NCp9 and NCp15 Suppress ATP-Mediated Rescue of AZT-Terminated Primers by HIV-1 Reverse Transcriptase. 3274 59