tailieunhanh - Báo cáo khoa học: Characterization of D-amino-acid-containing excitatory conotoxins and redefinition of the I-conotoxin superfamily

Post-translational isomerization ofl-amino acids to d-amino acids is a subtle modification, not detectable by standard techniques such as Edman sequencing or MS. Accurate predictions require more sequences of modi-fied polypeptides. A 46-amino-acid-long conotoxin, r11a, belonging to the I-superfamily was previously shown to have ad-Phe residue at position 44. | iFEBS Journal Characterization of D-amino-acid-containing excitatory conotoxins and redefinition of the I-conotoxin superfamily Olga Buczek1 Doju Yoshikami1 Maren Watkins2 Grzegorz Bulaj1 Elsie C. Jimenez1 3 and Baldomero M. Olivera1 1 Department of Biology and 2 Pathology University of Utah Salt Lake City UT 84112 USA 3 Department of PhysicalSciences College of Science University of the Philippines Baguio Baguio City Philippines Keywords conotoxin D-amino acid excitatory peptides post-translationalmodification repetitive action potential Correspondence B. M. Olivera Department of Biology University of Utah 257 South 1400 East Salt Lake City UT 84112 USA Tel 1 801 581 8370 Fax 1 801 585 5010 E-mail olivera@ Received 25 April 2005 revised 15 June 2005 accepted 21 June 2005 doi Post-translational isomerization of L-amino acids to D-amino acids is a subtle modification not detectable by standard techniques such as Edman sequencing or MS. Accurate predictions require more sequences of modified polypeptides. A 46-amino-acid-long conotoxin r11a belonging to the I-superfamily was previously shown to have a D-Phe residue at position 44. In this report we characterize two related peptides r11b and r11c with D-Phe and D-Leu respectively at the homologous position. Electrophysiological tests show that all three peptides induce repetitive activity in frog motor nerve and epimerization of the single amino acid at the third position from the C-terminus attenuates the potency of r11a and r11b but not that of r11c. Furthermore r11c but neither r11a nor r11b also acts on skeletal muscle. We identified more cDNA clones encoding conopeptide precursors with Cys patterns similar to r11a b c. Although the predicted mature toxins have the same cysteine patterns they belong to two different gene superfamilies. A potential correlation between the identity of the gene superfamily to which the I-conotoxin belongs and the presence or absence of

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