Handbook of Proteolytic Enzymes

Handbook of Proteolytic Enzymes (Second Edition)

Aspartic and Metallo Peptidases
2004, Pages 174-175
Handbook of Proteolytic Enzymes

49 - Mouse mammary tumor virus retropepsin

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This chapter describes the structural chemistry and the biological aspects of Mouse Mammary Tumor Virus (MMTV) retropepsin. MMTV are endogenous and exogenous retroviruses, mostly milkborne, which often cause mammary carcinomas and sometimes T-cell lymphomas. The MMTV retropepsin is commonly referred to as MMTV protease. MMTV retropepsin is a homodimeric enzyme formed by two 115 amino acid polypeptide chains. The MT of each subunit is 13,500 as estimated by SDS-PAGE. Maturation sites in Gag and Gag-Pro polyproteins have been inferred by comparison of their primary structure derived from the nucleotide sequence of the MMTV genome and the N- and C-terminal sequences of proteins purified from the mature virus. Synthetic oligopeptides, mimicking the maturation sites found in the gag-related polyproteins, are useful substrates to detect an MMTV retropepsin activity. MMTV retropepsin has been partially purified from a virus (strain C3H) obtained from the culture supernatants of infected cell lines such as MMT 060562 (ATCC CCL51) or Mm5mt/cl, but yields are very low.

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