MOLECULES AT THE EXTERNAL NUCLEAR SURFACE Sialic Acid of Nuclear Membranes and Electrophoretic Mobility of Isolated Nuclei and Nucleoli

نویسنده

  • H. BRUCE BOSMANN
چکیده

The molecules occurring as terminal residues on the external surfaces of nuclei prepared from rat liver by either sucrose-CaC12 or citric acid methods and nucleoli derived from the sucrose-CaC1 2 nuclei were studied chemically and electrokinetically . In 0.0145 M NaCl, 4.50/,) sorbitol, and 0 .6 mM NaHCO3 with pH 7 .2 t 0.1 at 25°C, the sucrose-CaC12 nuclei had an electrophoretic mobility of -1 .92 ,um/s/V/cm, the citric acid nuclei, -1 .63 μm/s/V/cm, and the nucleoli, -2 .53 μm/s/V/cm . The citric acid nuclei and the nucleoli contained no measurable sialic acid . The sucrose-CaC12 nuclei contained 0.7 pmol of sialic acid/mg nuclear protein ; this was essentially located in the nuclear envelope . Treatment of these nuclei with 50 μg neuraminidase/mg protein resulted in release of 0.63 pmol of sialic acid/mg nuclear protein ; treatment with 1 % trypsin caused release of 0 .39 nmol of the sialic acid/mg nuclear protein . The pH-mobility curves for the particles indicated the sucrose-CaC12 nuclei surface had an acid-dissociable group of pK 2.7 while the pK for the nucleoli was considerably lower . Nucleoli treated with 50 μg neuraminidase/mg particle protein had a mobility of -2 .53 Am/s/V/cm while sucrose-CaC12 nuclei similarly treated had a mobility of -1 .41 μm/s/V/cm. Hyaluronidase at 50 μg/mg protein had no effect on nucleoli mobility but decreased the sucrose-CaC12 nuclei mobility to -1 .79 M.m/s/V/cm . Trypsin at 1 % elevated the electrophoretic mobility of the sucrose-CaC12 nuclei slightly but decreased the mobility of the nucleoli to -2 .09 μm/s/V/cm. DNase at 50 Ag/mg protein had no effect on the mobility of the isolated sucrose-CaC12 nuclei but decreased the electrophoretic mobility of the nucleoli to -1 .21 μm/s/V/cm. RNase at 50 μg/mg protein also had no effect on the electrophoretic mobility of the sucrose-CaC12 nuclei but decreased the nucleoli mobility to -2 .10 μm/s/V/cm . Concanavalin A at 50 Ag/mg protein did not alter the nucleoli electrophoretic mobility but decreased the sucrose-CaC1 2 nuclei electrophoretic mobility to -1 .64 μm/s/V/cm . The results are interpreted to mean that the sucrose-CaC1 2 nuclear external surface contains terminal sialic acid residues in trypsin-sensitive glycoproteins, contains small amounts of hyaluronic acid, is completely devoid of nucleic acids, and binds concanavalin A . The nucleolus surface is interpreted to contain a complex made up of protein, RNA, and primarily DNA, to be devoid of sialic acid and hyaluronic acid, and not to bind concanavalin A. THE JOURNAL OF CELL BIOLOGY • VOLUME 59, 1978 . pages 6 0 1 -614 601 on Jauary 1, 2018 jcb.rress.org D ow nladed fom

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تاریخ انتشار 2003