Role of Thr(11) in the binding of omega-conotoxin MVIIC to N-type Ca2+ channels.
As replacement of Thr(11) of omega-conotoxin MVIIC with Ala significantly reduced the affinity for both N- and P/Q-type calcium channels, we examined the effect of substitution at this position with other residues. Binding assays using rat cerebellar P2 membranes showed that the affinity is in the order of Leu>Val, aminobutyric acid, Thr>Asn&z.Gt;Ser, Ala, Asp, Phe, Tyr for N-type channels and Thr>Leu, Val, aminobutyric acid, Asn, Ser>Ala&z.Gt;Asp, Phe, Tyr for P/Q-type channels, suggesting that aliphatic amino acids with longer side chains are favorable for block of N-type channels. The effects of substitution were examined electrophysiologically in BHK cells expressing N-type Ca2+ channels. Inhibition of Ba2+ current by the analogs did not completely correlate with binding affinity, although binding to BHK cells was comparable to rat cerebellar membranes.
Mitsubishi Kasei Institute of Life Sciences, 11 Minamiooya, Machida, Tokyo 194-8511, Japan.
K
K
Minami
C
C
Raymond
N
N
Martin-Moutot
A
A
Ohtake
C
C
Van Renterghem
M
M
Takahashi
M J
MJ
Seagar
Y
Y
Mori
K
K
Sato
D000409:Alanine / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D001464:Barium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000737:chemistry / Q000378:metabolism*; D020864:Calcium Channels, N-Type / Q000737:chemistry / Q000378:metabolism*; D020865:Calcium Channels, P-Type / Q000737:chemistry / Q000378:metabolism; D020907:Calcium Channels, Q-Type / Q000737:chemistry / Q000378:metabolism; D002478:Cells, Cultured; D006224:Cricetinae; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D011485:Protein Binding; D051381:Rats; D013912:Threonine / Q000737:chemistry*; D020960:omega-Conotoxins / Q000737:chemistry / Q000378:metabolism*
D002121:Calcium Channel Blockers; D020864:Calcium Channels, N-Type; D020865:Calcium Channels, P-Type; D020907:Calcium Channels, Q-Type; D020960:omega-Conotoxins; C075851:omega-conotoxin-MVIIC; D001464:Barium; D013912:Threonine; D000409:Alanine