Browsing by Author "MENDEZ, B"

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    ACETYLCHOLINESTERASE AGGREGATES IN A NEWLY FORMED MOTOR-NERVE SMOOTH-MUSCLE JUNCTION
    (1981) MENDEZ, B; INESTROSA, NC
    The changes in acetylcholinesterase (AChE) molecular forms were studied during cross-innervation of the inferior smooth muscle of the cat nictitating membrane by the hypoglossal nerve. One month after functional cross-innervation AChE activity increased by 2-fold above control values, and a new high MW AChE form (A12) was detected. BW284c51 [1,5-bis-(4-allyldimethylammoniumphenyl)-pentan-3-one dibromide], an anti-AChE, potentiated the contraction of the cross-innervated smooth muscle. AChE activity raised 6-fold above normal values 3 mo. later. At this time, half of the activity sediments to the bottom of the sucrose gradient and a time-dependent dissociation occurs in lighter AChE forms, reminiscent of AChE aggregates observed in the electric eel [Electrophorus electricus]. The multimolecular aggregates may be involved in the immobilization of AChE at the neuromuscular junction of a motor nerve and a smooth muscle.
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    CELL-FREE SYNTHESIS OF ACETYLCHOLINE-RECEPTOR POLYPEPTIDES
    (1980) MENDEZ, B; VALENZUELA, P; MARTIAL, JA; BAXTER, JD
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    CREATINE-KINASE PROTEIN-SEQUENCE ENCODED BY A CDNA MADE FROM TORPEDO-CALIFORNICA ELECTRIC ORGAN MESSENGER-RNA
    (1984) WEST, BL; BABBITT, PC; MENDEZ, B; BAXTER, JD
    Creatine kinase (ATP creatine N-phosphotransferase, EC 2.7.3.2) is important in the maintenance of ATP levels in high energy-requiring tissues such as muscle and brain. A complete understanding of its function requires knowledge of its amino acid sequence. To obtain cDNA [complementary DNA] clones encoding creatine kinase sequences, a cDNA bank was constructed using mRNA from the electric organ of T. californica and was screened by comparing differential colony hybridization of electric organ and liver-derived 32P-labeled cDNA. Cloned DNA were isolated that can arrest the abundant synthesis of MW 40,000-43,000 material seen after in vitro translation of electric organ mRNA. One of the clones, CK52g8, was sequenced by the dideoxy M13 method and was found to encode a MW 42,941 protein, which is 68% homologous to a known partial sequence of rabbit muscle creatine kinases and which has a composition similar to creatine kinases from chicken and rabbit tissues. By contrast, no significant homology was found with the known sequences of kinases that use other substrates. RNA blot hybridization analysis indicated that CK52g8 is complementary to a 1600-base-pair mRNA. Primer extension analysis indicated that CK52g8 is only 5 nucleotides short of a full-length cDNA, implying that it encodes a complete protein sequence. The availability of this complete sequence should be useful in further studies of creatine kinase structure and function using techniques such as site-specific mutagenesis.
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    THE A12 ACETYLCHOLINESTERASE AND POLYPEPTIDE COMPOSITION OF ELECTRIC ORGAN BASAL LAMINA OF ELECTROPHORUS AND SOME TORPEDINAE FISHES
    (1983) INESTROSA, NC; MENDEZ, B
    Basal lamina (BL) of Torpedo, Discopyge and Electrophorus electric organs was purified in order to establish polypeptide composition and association with acetylcholinesterase (AChE). BL apparently presents a distinct peptide pattern and that the A12 form of AChE is directly attached to it. Comparison of the species studied demonstrated similarities both in polypeptide composition and AChE content of the purified BL. Extractions of BL with solutions of high ionic strength, guanidine-HCl and acetic acid indicated the differential solubilization of various domains of BL polypeptides.
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    THE ELECTRIC ORGAN OF DISCOPYGE-TSCHUDII - ITS INNERVATED FACE AND THE BIOLOGY OF ACETYLCHOLINESTERASE
    (1984) MENDEZ, B; GARRIDO, J; MALDONADO, M; JAKSIC, FM; INESTROSA, NC
    An ultrastructural, histochemical and biochemical study of the electric organ of the South American Torpedinid ray. D. tschudii was carried out. Fine structural cytochemical localization of acetylcholinesterase (AChE) indicated that most of the esterase was associated with the basal lamina. EM indicated no marked differences in the electrocyte ultrastructure between Discopyge and Torpedo californica. Discopyge electric organ possessed 3 molecular forms, 2 asymmetric forms (16 S and 13 S) and 1 globular hydrophobic form (6.5 S). The asymmetric 16 S AChE form was solubilized by heparin, a sulfated glycosaminoglycan, suggesting that heparin-like macromolecules are involved in the binding of the enzyme to the basal lamina. Cell-free translated AChE peptides, synthesized using Discopyge electric organ poly(A+) RNA, correspond to a main band of 62,000 daltons which probably represents the catalytic subunit of the asymmetric AChE.