H-1-NMR and circular dichroism spectroscopic studies on changes in secondary structures of the sodium channel inactivation gate peptides as caused bythe pentapeptide KIFMK

Citation
Y. Kuroda et al., H-1-NMR and circular dichroism spectroscopic studies on changes in secondary structures of the sodium channel inactivation gate peptides as caused bythe pentapeptide KIFMK, BIOPHYS J, 77(3), 1999, pp. 1363-1373
Citations number
40
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
BIOPHYSICAL JOURNAL
ISSN journal
0006-3495 → ACNP
Volume
77
Issue
3
Year of publication
1999
Pages
1363 - 1373
Database
ISI
SICI code
0006-3495(199909)77:3<1363:HACDSS>2.0.ZU;2-K
Abstract
The pentapeptide KIFMK, which contains three clustered hydrophobic amino ac id residues of isoleucine, phenylalanine, and methionine (IFM) in the sodiu m channel inactivation gate on the cytoplasmic linker between domains III a nd IV (III-IV linker), is known to restore fast inactivation to the mutant sodium channels having a defective inactivation gate or to accelerate the i nactivation of the wild-type sodium channels. To investigate the docking si te of KIFMK and to clarify the mechanisms for restoring the fast inactivati on, we have studied the interactions between KIFMK and the fragment peptide in the III-IV linker GGQDIFMTEEQK (MP-1A; G1484-K1495 in rat brain IIA) by one- and two-dimensional H-1-NMR and circular dichroism (CD) spectroscopie s. KIFMK was found to increase the helical content of MP-1A in 80% trifluor oethanol (TFE) solution by similar to 11%. A pentapeptide, KIFMT, which can restore inactivation but less effectively than KIFMK, also increased the h elical content of MP-1A, but to a lesser extent (similar to 6%) than did KI FMK. In contrast, KDIFMTK, which is ineffective in restoring inactivation, decreased the helical content (similar to-4%). Furthermore, we studied the interactions between KIFMK and modified peptides from MP-1A, that is, MP-1N A (D1487N), MP-1QEA (E1492Q), or MP-1EQA (E1493Q). The KIFMK was found to i ncrease the helical content of MP-1EQA to an extent nearly identical to tha t of MP-1A, whereas it was found to decrease those of MP-1NA and MP-1QEA. T hese findings mean that KIFMK, by allowing each of the Lys residues to inte ract with D1487 and E1492, respectively, stabilized the helical structure o f the Ill-IV linker around the IFM residues. This helix-stabilizing effect of KIFMK on the III-IV linker may restore and/or accelerate fast inactivati on to the sodium channels having a defective inactivation gate or to wild-t ype sodium channels.