title: Calcium transport by ionophorous peptides in dog and human lymphocytes detected by quin-2 fluorescence.
abstract: Synthetic peptides of structure cyclo(Glu(OBz)-Sar-Gly-(N-R)Gly)2 (I), electrogenic Ca2+-selective carriers in phospholipid vesicle membranes, are shown to mediate the uptake of Ca2+ ions into the cytoplasm of dog and human lymphocytes. Ca2+ transport by DECYL-2E (I, R = n-decyl) - monitored by measurements of the fluorescence of an intracellular dye, quin-2 - occurred at a rate comparable to that produced by electroneutral Ca2+ ionophores ionomycin and Br-A23187. Fluorescence quenching experiments using Mn2+ suggested a greater selectivity by DECYL-2E for Ca2+/Mn2+ vs. the other two ionophores. The result that Ca2+ ions can traverse biological membranes bound in a neutral cavity consisting exclusively of peptide carbonyl ligands may imply the functional significance of binding sites of similar structures in membrane transport proteins.
mesh_terms: D000634:Aminoquinolines; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D004285:Dogs; D005109:Extracellular Matrix / Q000378:metabolism; D006801:Humans; D007476:Ionophores / Q000378:metabolism*; D008214:Lymphocytes / Q000378:metabolism*; D008345:Manganese / Q000378:metabolism; D010456:Peptides, Cyclic / Q000378:metabolism*
chemical_list: D000634:Aminoquinolines; D007476:Ionophores; D010456:Peptides, Cyclic; D008345:Manganese; C047928:cyclo(Glu(O-benzyl)-Sar-Gly-(N-n-decyl)Gly)2; C035738:Quin2-acetoxymethyl ester; D002118:Calcium