Effects of recombinant neurotoxins on single Na(+) channels in isolated rat hippocampal neurons.
Four recombinant neurotoxins Hk2a, Hk7a, Hk8a, Hk16a, originally from a sea anemone species Anthopleura sp., were obtained by fusion expression of their genes in Escherichia coli. These neurotoxins were composed of 47 amino acid residues, among which the differences were found at positions 14, 22, 25, and 37, respectively. The effects of the four neurotoxins on single-channel current of sodium in rat hippocampal neurons were studied by cell-attached patch clamp. Each neurotoxin 2 microM could modulate the sodium channel by prolonging the opening dwell time and increasing the open probability, but did not change the amplitude of sodium channel currents. Based on the studies of the structure-function relationship, we found that Hk7a displayed the biggest increase of the open probability because His14 (from Arg14) makes its structure seem more compact in comparison with the other three toxins and Ap-A. Phe25 (Hk8a, Hk16a), which varied from Ala25 (Hk2a, Hk7a), showed that phenyl group might interfere with other key amino acid residue to decrease the activity of toxins. Arg37 (from His37) in Hk8a contributed to decrease of open probability. In our work, it was shown that these important amino acid sites might provide a reliable proof for the future pharmaceutical design.
Xiang
Hui
H
Department of Biological Science and Technology, Sun Yat-sen, Zhongshan University, Guangzhou, Guangdong Province, People's Republic of China. lssxh@mail.sysu.edu.cn
Wang
Lei
L
Cui
Jihong
J
Du
Jianyang
J
Wang
Ke
K
Xu
Anlong
A
D000595:Amino Acid Sequence; D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects; D002469:Cell Separation; D006624:Hippocampus / Q000166:cytology*; D015640:Ion Channel Gating / Q000187:drug effects; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D009498:Neurotoxins / Q000737:chemistry / Q000633:toxicity*; D051381:Rats; D011994:Recombinant Proteins / Q000633:toxicity*; D012615:Sea Anemones / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015222:Sodium Channels / Q000378:metabolism*; D013997:Time Factors
D009498:Neurotoxins; D011994:Recombinant Proteins; D015222:Sodium Channels