Document 0832
 DOCN  M9590832
 TI    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.
 DT    9509
 AU    Fan N; Rank KB; Leone JW; Heinrikson RL; Bannow CA; Smith CW; Evans DB;
       Poppe SM; Tarpley WG; Rothrock DJ; et al; Upjohn Laboratories,
       Kalamazoo, Michigan 49001, USA.
 SO    J Biol Chem. 1995 Jun 2;270(22):13573-9. Unique Identifier : AIDSLINE
       MED/95286657
 AB    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.
 DE    Amino Acid Sequence  Cloning, Molecular  Hydrolysis  HIV
       Protease/*METABOLISM  HIV-1/*ENZYMOLOGY  HIV-2/*ENZYMOLOGY  Molecular
       Sequence Data  Peptides/METABOLISM  Protein Processing,
       Post-Translational  Reverse Transcriptase/GENETICS/*METABOLISM  Sequence
       Homology, Amino Acid  Substrate Specificity  Support, U.S. Gov't, P.H.S.
       JOURNAL ARTICLE

       SOURCE: National Library of Medicine.  NOTICE: This material may be
       protected by Copyright Law (Title 17, U.S.Code).