The Pr65gag proteolytic factor obtained from Moloney (MoLV) or Rauscher (RLV) leukaemia virus has been characterized. We found that it was present in small amounts in virions and was extremely unstable. Although it eluted at the trailing edge of p12 on Sephadex G-75 columns, it could clearly be separated from p12 on DEAE-Sephadex A-50M columns, making it unlikely that the factor is p12 or any other major murine leukaemia virus (MuLV) protein. This fact also distinguishes the murine factor from the avian p15-associated protease which is present in large amounts in avian tumour viruses and is stable to column purification methods (von der Helm, 1977; Dittmar & Moelling, 1978). We further observed that: (i) the murine proteolytic factor had an estimated mol. wt. of 20000 to 22000, relative to MuLV p12, which eluted as a dimer on Sephadex G-75 columns in the presence of 0.1% NP-40; and (ii) in vitro cleavage of an iodinated Pr65gag-rich, p30-deficient substrate yielded a clear increase in both p30 and p12, which suggests that the in vitro cleavage of Pr65gag is similar to its processing in vivo.
BurnetteW. N.,
HolladayL. A.,
MitchellW. M.1976; Physical and chemical properties of Moloney murine leukemia virus P30 protein: a major core structural component exhibiting high helicity and selfassociation. Journal of Molecular Biology 107:131–143
IkedaH.,
HardyW.Jun,
TressE.,
FleissnerE.1975; Chromatographic separation and antigenic analysis of proteins of the oncornaviruses. V. Identification of a new murine viral protein, pi5(E). Journal of Virology 16:53–61
JamjoomG. A.,
NasoR. B.,
ArlinghausR. B.1977; Further characterization of intracellular precursor polyproteins of Rauscher leukemia virus. Virology 78:11–34
JohnsonR. W.,
PerryA.,
RobinsonO. R.Jun,
ShibleyG. P.1976; Method for reproducible large-volume production and purification of Rauscher murine leukemia virus. Applied Environmental Microbiology 31:182–188
PalB. K.,
McallisterR. M.,
GardnerM. B.,
Roy-BurmanP.1975; Comparative studies on the structural phosphoproteins of mammalian type-C viruses. Journal of Virology 16:123–131
SchultzA. M.,
OroszlanS.1978; Murine leukemia virus gag polyproteins: the peptide chain unique to Pr8o is located at the amino terminus. Virology 91:481–486
SchultzA. M.,
RabinE. H.,
OroszlanS.1979; Post-translational modification of Rauscher leukemia virus precursor polyproteins encoded by the gag gene. Journal of Virology 30:255–266
VogtV. M.,
EisenmanR.,
DiggelmannH.1975; Generation of AMV structural proteins by proteolytic cleavage of a precursor polypeptide. Journal of Molecular Biology 96:471–493
Von Der HelmK.1977; Cleavage of Rous sarcoma viral polypeptide precursor into internal structural proteins in vitro involves viral protein P15. Proceedings of the National Academy of Sciences of the United States of America 74:911–915
YoshinakaY.,
LuftigR. B.1977b; Murine leukemia virus morphogenesis cleavage of P70 can be accompanied by a morphological conversion from an immature to a mature form of the core. Proceedings of the National Academy of Sciences of the United States of America 74:3446–3450
YoshinakaY.,
LuftigR. B.1977c; Partial purification of a P70 proteolytic factor that is present in purified virions of Rauscher leukemia virus (RLY). Biochemical and Biophysical Research Communications 76:54–63
YoshinakaY.,
LuftigR. B.1977d; Characterization of Rauscher leukemia virus (RLV) P40-42, an intermediate cleavage product of the group specific antigen (gag) precursor polypeptide, P65-70. Biochemical and Biophysical Research Communications 79:319–325
YoshinakaY.,
LuftigR. B.1978; Morphological conversion of ‘immature’ Rauscher leukaemia virus cores to a ‘mature’ form after addition of the P65-70 (gag gene product proteolytic factor). Journal of General Virology 40:151–160