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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

The differential processing of homodimers of reverse transcriptases from human immunodeficiency viruses type 1 and 2 is a consequence of the distinct specificities of the viral proteases.

Active, recombinant p68 reverse transcriptase ( RT) from human immunodeficiency virus type 2 (HIV-2), with an NH2-terminal extension containing a hexahistidine sequence was isolated from extracts of Escherichia coli by immobilized metal affinity chromatography. Treatment of the purified p68/p68 homodimer of HIV-2 RT with recombinant HIV-2 protease generates stable, active heterodimer (p68/ p58) that is resistant to further hydrolysis. Analysis of this p68/ p58 HIV-2 RT heterodimer revealed that while one subunit is intact p68, the p58 subunit is COOH-terminally truncated by cleavage, not at Phe440 as is seen in processing of the p66/p66 HIV-1 RT homodimer by HIV-1 protease, but at Met484. The expected COOH-terminal p10 fragment resulting from hydrolysis of p68 at Met484 is not released intact, but undergoes further cleavage at Asn494, Met503, and Tyr532. Processing of p68/p68 HIV-2 RT with the HIV-1 protease led to cleavage of the Phe440-Tyr441 bond, exactly as is seen with p66/p66 HIV-1 RT, to give the analogous p53 subunit. Studies of a peptide substrate modeled after residues 437-444 in HIV-2 RT showed that while the HIV-1 protease was able to cleave the Phe440 bond, this bond was resistant to cleavage by the HIV-2 enzyme. Our findings provide a rationale for the previous observation that the RT heterodimer isolated from HIV-2 lysates is larger than that from HIV-1. We conclude that the p68/ p58 HIV-2 RT heterodimer, containing the Met484 truncated p58 subunit, is a biologically relevant form of the enzyme in vivo.[1]

References

  1. The differential processing of homodimers of reverse transcriptases from human immunodeficiency viruses type 1 and 2 is a consequence of the distinct specificities of the viral proteases. Fan, N., Rank, K.B., Leone, J.W., Heinrikson, R.L., Bannow, C.A., Smith, C.W., Evans, D.B., Poppe, S.M., Tarpley, W.G., Rothrock, D.J. J. Biol. Chem. (1995) [Pubmed]
 
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