title: Kinetic variations between reverse transcriptases of viral protein X coding and noncoding lentiviruses.
abstract: BACKGROUND
  Host SAM domain and HD domain-containing protein 1 (SAMHD1) suppresses reverse transcription kinetics of HIV-1 in nondividing cells such as macrophages by hydrolyzing and nearly depleting cellular dNTPs, which are the substrates of viral reverse transcriptase (RT). However, unlike HIV-1, HIV-2 and SIVsm encode viral protein X (Vpx), which counteracts the dNTPase activity of SAMHD1 and elevates dNTP concentration, allowing the viruses to replicate under abundant dNTP conditions even in nondividing cells.
  
  
  RESULTS
  Here we tested whether RTs of these Vpx coding and noncoding lentiviruses display different enzyme kinetic profiles in response to dNTP concentrations. For this test, we characterized an extensive collection of RTs from 7 HIV-1 strains, 4 HIV-2 strains and 7 SIV strains, and determined their steady-state kinetic parameters. The K m values of all HIV-1 RTs were consistently low and close to the low dNTP concentrations found in macrophages. However, the K m values of SIV and HIV-2 RTs were not only higher than those of HIV-1 RTs but also varied significantly, indicating that HIV-2/SIV RTs require higher dNTP concentrations for efficient DNA synthesis, compared to HIV-1 RT. However, the k cat values of all eighteen lentiviral RTs were very similar.
  
  
  CONCLUSIONS
  Our biochemical analysis supports the hypothesis that the enzymological properties, particularly, K m values, of lentivirus RTs, are mechanistically tied with the cellular dNTP availability in nondividing target cells, which is controlled by SAMHD1 and Vpx.
authors.affiliation: Center for Drug Discovery, Center for AIDS Research, Department of Pediatrics, Emory University School of Medicine, 1760 Haygood Drive, Atlanta, GA, USA. glenzi@emory.edu.
authors.forename: Gina M
authors.initials: GM
authors.lastname: Lenzi
authors.affiliation: Center for Drug Discovery, Center for AIDS Research, Department of Pediatrics, Emory University School of Medicine, 1760 Haygood Drive, Atlanta, GA, USA. robert.domaoal@emory.edu.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Domaoal
authors.affiliation: College of Pharmacy, Kyung-Hee University, Seoul, South Korea. dhkim@khu.ac.kr.
authors.forename: Dong-Hyun
authors.initials: DH
authors.lastname: Kim
authors.affiliation: Center for Drug Discovery, Center for AIDS Research, Department of Pediatrics, Emory University School of Medicine, 1760 Haygood Drive, Atlanta, GA, USA. rschina@emory.edu.|Veterans Affairs Medical Center, Decatur, GA, USA. rschina@emory.edu.
authors.forename: Raymond F
authors.initials: RF
authors.lastname: Schinazi
authors.affiliation: Center for Drug Discovery, Center for AIDS Research, Department of Pediatrics, Emory University School of Medicine, 1760 Haygood Drive, Atlanta, GA, USA. baek.kim@emory.edu.|College of Pharmacy, Kyung-Hee University, Seoul, South Korea. baek.kim@emory.edu.
authors.forename: Baek
authors.initials: B
authors.lastname: Kim
mesh_terms: D015497:HIV-1 / Q000201:enzymology*; D015498:HIV-2 / Q000201:enzymology*; D007700:Kinetics; D009711:Nucleotides / Q000378:metabolism; D012194:RNA-Directed DNA Polymerase / Q000378:metabolism*; D015302:Simian Immunodeficiency Virus / Q000201:enzymology*
chemical_list: D009711:Nucleotides; D012194:RNA-Directed DNA Polymerase