title: Brain cysteine proteinase inhibitors II: evidence that a 21-kDa papain-binding component resembles ras p21.
abstract: A 21-kDa protein extracted from rat or bovine brain at high pH was purified on alkylated-papain and shown to have dual ras-like and cysteine proteinase inhibitory (CPI) properties. This was demonstrated by its GTP-binding activity, cross-reactivity toward pan-reactive ras p21 monoclonal antibody, and inhibition of papain. The material eluted earlier than cystatins or kininogens on the alkylated papain-affinity column and was devoid of other CPIs based on immunoblot analysis. In a second procedure, ras p21s isolated from rat or bovine brain membranes by cholate extraction and purified by gel-permeation and hydrophobic interaction were shown to act also as potent CPIs, inhibiting rat brain cathepsin L, papain, or rat brain cathepsin B with Ki values of 3, 11, and 167 nM, respectively. This component cross-reacted with the monospecific anti-ras, but not with other anti-CPIs, and represented 3-4% of total GTP binding present in homogenates. The specific activity of the purified 21 kDa component was 4.7 nmol GTP-gamma-S bound per mg protein. The data support the notion that brain ras p21s constitute a separate group of CPIs and are available for regulating some aspects of brain protein turnover.
authors.affiliation: Nathan Kline Institute for Psychiatric Research, Center for Neurochemistry, Orangeburg, New York 10962.
authors.forename: M J
authors.initials: MJ
authors.lastname: Berg
authors.forename: N
authors.initials: N
authors.lastname: Marks
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D001923:Brain Chemistry / Q000502:physiology*; D056668:Cathepsin L; D002403:Cathepsins / Q000096:biosynthesis; D002417:Cattle; D003546:Cysteine Endopeptidases; D015853:Cysteine Proteinase Inhibitors / Q000378:metabolism*; D003902:Detergents; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D008969:Molecular Sequence Data; D015689:Oncogene Protein p21(ras) / Q000378:metabolism*; D010206:Papain / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats
chemical_list: D015853:Cysteine Proteinase Inhibitors; D003902:Detergents; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D002403:Cathepsins; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; D056668:Cathepsin L; C534280:Ctsl protein, rat; D010206:Papain; D015689:Oncogene Protein p21(ras)