Analysis of gag proteins from mouse mammary tumor virus

A. Hizi, L. E. Henderson, T. D. Copeland, R. C. Sowder, H. C. Krutzsch, S. Oroszlan

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Abstract

Structural proteins designated p10(gag), p21(gag), p8(gag), p3(gag), p27(gag), and p14(gag) from the C3H strain of mouse mammary tumor virus (MMTV) were purified by reversed-phase high-pressure liquid chromatography. The N- and C-terminal amino acid sequences and amino acid composition of each protein were determined and compared with the amino acids encoded by the proviral DNA sequences for the MMTV gag gene. The results show that each of the purified proteins is a proteolytic cleavage product derived from the predicted primary translational product of the gag gene (Pr77(gag)) and that their order in Pr77(gag) is p10-pp21-p8-p3-n-p27-p14 (where n represents 17 predicted residues that were not identified among the purified proteins). Purified p10(gag) lacks the initiator methionine and has a myristoyl group attached in amide linkage to the N-terminal glycine residue predicted by the second codon of the gag gene. The cleavage products are contiguous in the sequence of Pr77(gag), and the C-terminal residue of p14(gag) is encoded by the last codon of the gag gene. By analogy with other retroviruses, p14(gag) is the viral nucleocapsid protein, p10(gag) is the matrix protein, and p27(gag) is the capsid protein of mature MMTV. Proteolytic cleavage sites in MMTV Pr77(gag) bear a striking resemblance to cleavage sites in the gag precursors of D-type retroviruses, suggesting that these viral proteases have similar specificities.

Original languageEnglish
Pages (from-to)2543-2549
Number of pages7
JournalJournal of Virology
Volume63
Issue number6
DOIs
StatePublished - 1989
Externally publishedYes

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