title: Enzymatic properties, metal composition and SH-group reactivity of the light and heavy sarcoplasmic reticulum vesicles.
abstract: Light (LT) and heavy (TTC) microsomes were isolated from the fragmented sarcoplasmic reticulum (FSR) of rabbit skeletal muscle by sucrose gradient centrifugation. The amount of the protein components (ATPase, "feet proteins", calsequestrine) showed substantial differences between the light and heavy fractions. The amounts of calcium, magnesium and zinc were about 2-4 times higher in the TTC fraction, then those of the LT fraction. The activities of the Ca2+ + Mg2+ activated para-nitrophenyl-phosphatase and acetylcholin-esterase were (about 1.5 times) also higher in the TTC fraction compared to the LT fraction. The ratio of the Ca-transport vs. ATP was 2.1 in case of the LT and 0.6 in case of the TTC fraction. The number of titerable SH-groups of the LT fraction, measured in EGTA-medium containing Ca2+, was higher than those measured in the absence of Ca2+, while for the TTC fraction this number was higher when determined in the absence of Ca2+. We suppose that due to the higher amount of Ca2+ and Zn2+ in the TTC fraction those SH-groups which were present as Ca- or Zn-thiolates became titerable in EGTA-medium in the absence of Ca2+.
authors.affiliation: Central Research Laboratory, University Medical School, Debrecen, Hungary.
authors.forename: M
authors.initials: M
authors.lastname: Szabolcs
authors.forename: I
authors.initials: I
authors.lastname: Jóna
authors.forename: S
authors.initials: S
authors.lastname: Varga
mesh_terms: D009597:4-Nitrophenylphosphatase / Q000378:metabolism; D000110:Acetylcholinesterase / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000032:analysis / Q000493:pharmacokinetics; D002458:Cell Fractionation; D006867:Hydrolases / Q000378:metabolism; D008274:Magnesium / Q000032:analysis; D008670:Metals / Q000737:chemistry* / Q000493:pharmacokinetics; D008861:Microsomes / Q000737:chemistry; D011506:Proteins / Q000378:metabolism; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000737:chemistry* / Q000201:enzymology* / Q000648:ultrastructure; D013329:Structure-Activity Relationship; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D015032:Zinc / Q000032:analysis
chemical_list: D008670:Metals; D011506:Proteins; D013438:Sulfhydryl Compounds; D006867:Hydrolases; D000110:Acetylcholinesterase; D009597:4-Nitrophenylphosphatase; D000251:Adenosine Triphosphatases; D008274:Magnesium; D015032:Zinc; D002118:Calcium