Omega-agatoxin-TK containing D-serine at position 46, but not synthetic omega-[L-Ser46]agatoxin-TK, exerts blockade of P-type calcium channels in cerebellar Purkinje neurons.
omega-Agatoxin-TK (omega-Aga-TK), a 48-amino-acid peptide isolated from the venom of the funnel web spider (Agelenopsis aperta), is a selective and potent inhibitor of P-type calcium channels in the nervous system. We have synthesized a peptide that has the amino acid sequence identified for native omega-Aga-TK. The synthetic omega-Aga-TK, however, showed 80-90-fold less potent inhibition of P-type calcium channels, compared with native omega-Aga-TK. Enantiomer analysis of native omega-Aga-TK revealed D-serine at position 46, and synthetic omega-[D-Ser46]Aga-TK had the same potency as native omega-Aga-TK for blocking P-type calcium channels in cultured cerebellar Purkinje neurons. Two peptide fragments of omega-Aga-TK, namely omega-Aga-TK(1-43) and the carboxyl-terminal peptide fragment omega-Aga-TK(44-48), did not produce any significant inhibition of P-type calcium channels or interfere with the blockade of the channels elicited by native omega-Aga-TK. Molecular dynamics calculations showed that the carboxyl-terminal, six-amino-acid peptide of omega-Aga-TK containing D-Ser46 assumes a different conformation than does the peptide containing L-Ser46. These results suggest that the specific conformation of the carboxyl-terminal region of omega-Aga-TK, particularly the configuration of Ser46, together with a beta-sheet structure formed by four disulfide bonds, might be essential for blockade of P-type calcium channels.
Eisai Tsukuba Research Laboratory, Ibaraki, Japan.
M
M
Kuwada
T
T
Teramoto
K Y
KY
Kumagaye
K
K
Nakajima
T
T
Watanabe
T
T
Kawai
Y
Y
Kawakami
T
T
Niidome
K
K
Sawada
Y
Y
Nishizawa
D060848:Agatoxins; D000595:Amino Acid Sequence; D000818:Animals; D002121:Calcium Channel Blockers / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D002531:Cerebellum / Q000187:drug effects* / Q000378:metabolism; D006868:Hydrolysis; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000494:pharmacology; D011487:Protein Conformation; D011689:Purkinje Cells / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012694:Serine / Q000737:chemistry*; D013111:Spider Venoms / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D013329:Structure-Activity Relationship
D060848:Agatoxins; D002121:Calcium Channel Blockers; D010446:Peptide Fragments; D013111:Spider Venoms; C083855:omega-agatoxin-Aa4b; D012694:Serine