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N-myristoyltransferase1 and N-myristoyltransferase2 Exhibit Differential Substrate Specificity for HIV-Gag and HIV-Nef
Retrovirologyvolume 2, Article number: P88 (2005)
N-terminal myristoylation of Gag and Nef plays a critical role in retroviral virulence and budding of newly formed particles. Myristoylation involves the transfer of a myristate moiety from myristoyl-CoenzymeA (myristoyl-CoA) to substrate proteins such as Gag and Nef. Two isozymes accomplish this process in humans, and are known as N-myristoyltransferase1 (NMT1) and N-myristoyltransferase2 (NMT2). We used a biochemical approach to determine myristoylation kinetics for Gag and Nef as well as preferential substrate specificity for NMT1 or NMT2.
Materials and methods
NBD-labeled peptides containing the myristoylation sequence for Gag or Nef were myristoylated by recombinant NMT1 or NMT2 and subsequently analyzed by HPLC analysis.
Results of the kinetics studies (Km, Kcat, catalytic efficiency, turnover number, etc.) indicate that both isozymes prefer Nef up to 150 times vs. Gag as a substrate. Both isozymes also exhibit greater catalytic efficiency in myristoylating Nef. Interestingly, Nef is preferentially myristoylated when Gag is present in the system.
This study is the first report of a differential role of NMT1 and NMT2 in the myristoylation of retroviral proteins and provides a new target in the treatment of HIV.