Fractionation of two protein kinases from avian myeloblastosis virus and characterization of the protein kinase activity preferring basic phosphoacceptor proteins

Abstract

Two protein kinase activities were fractionated from purified virions of avian myeloblastosis virus. Distinguishing characteristics of these two protein kinases included: (i) their binding properties during purification by ion-exchange chromatography; (ii) their estimated molecular weights; and (iii) their phosphoacceptor protein specificities. The protein kinase that bound to the anion exchanger DEAE-cellulose (pH 7.2) had an estimated molecular weight of 60,000 to 64,000 and preferred basic phosphoacceptor proteins. The protein kinase that bound to the cation exchanger phosphocellulose (pH 7.2) had an estimated molecular weight of 42,000 to 46,000 and preferred acidic phosphoacceptor proteins. The protein kinase preferring basic phosphoacceptor proteins was further purified and characterized. Optimal transfer of phosphate catalyzed by this enzyme required a divalent metal ion, a sulfhydryl-reducing agent, and ATP as phosphate donor. GTP was not an effective phosphate donor at concentrations comparable to ATP; and the cyclic nucleotides cyclic AMP and cyclic GMP neither stimulated nor inhibited protein phosphorylation by the protein kinase. The specificity of the protein kinase for basic phosphoacceptor proteins extended to proteins from avian myeloblastosis virus, in that the neutral to basic virion proteins p12, p19, and p27 served as phosphate acceptors. In addition, the protein kinase also appeared to phosphorylate itself. The role(s) of this virion-associated protein kinase is discussed.

Analysis of secondary modifications of mouse mammary tumor virus proteins by two-dimensional gel electrophoresis

“…Specific proteases for cleavage of the gag precursors have also been detected in virion particles (46). A functional requirement for phosphorylation during the budding of enveloped viruses also explains the ubiquitous presence of protein kinase activities in enveloped viruses (12,13,31,40). The MMTV virion protein kinase has a high affinity for one part of the gag precursor, namely p21.…”

Isolation of a protein kinase induced by herpes simplex virus type 1

“…Herpes simplex virus type 1 (HSV-1), a DNA virus with oncogenic potential, has been shown to contain an envelope-associated cyclic AMP-independent protein kinase (16a, 23). Other enveloped viruses, as well as adenovirus and vaccinia virus, have also been shown to have virion-associated protein kinases (1,3,8,9,12,14,20,22,(27)(28)(29). With respect to HSV-1, it is not known whether the virion-associated enzyme is virus coded or whether it is a host cell component acquired during either virus assembly or the budding process.…”

v-Src enhances phosphorylation at Ser-282 of the Rous sarcoma virus integrase

“…These include pp74c-raf and a 42-kDa serine/threonine kinase (2). Several kinases of various molecular weights and substrate preferences have been isolated from avian retroviruses (1, 6, 14,20). There is currently not enough evidence to predict whether any of these kinases is responsible for phosphorylation of IN and ,B.…”

“…Like proteolytic processing, phosphorylation occurs within the virion after budding (3) but is the result of a host kinase. The virion-associated kinase responsible for phosphorylation of IN and 1 has not been identified, although several kinases have been purified from RSV and avian myeloblastosis virus (AMV) (14,20). It is unclear whether phosphorylation directly affects the enzymatic properties of IN or RT (11,18,19).…”