title: A region of calpastatin domain L that reprimes cardiac L-type Ca2+ channels.
abstract: Calpastatin, an endogenous inhibitor of calpain, is composed of domain L and four repetitive homologous domains 1-4. Domains 1-4 inhibit calpain, whereas domain L partially reprimes L-type Ca2+ channels for voltage-gated activation. In the present study, the effects on Ca2+ channel activity of four isoforms and a series of fragments of calpastatin domain L were investigated in guinea-pig ventricular myocytes with the patch-clamp method. With one exception, all the isoforms and fragment peptides that contained amino acid residues 54-64 of domain L reprimed the Ca2+ channels to comparable levels (9-15% of control activity) to those observed previously with a full-length form of calpastatin. These results suggest that the region containing amino acid residues 54-64 (EGKPKEHTEPK) is responsible for the Ca2+ channel repriming function of calpastatin domain L.
authors.affiliation: Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Sakuragaoka 8-35-1, Kagoshima 890-8544, Japan.
authors.forename: Etsuko
authors.initials: E
authors.lastname: Minobe
authors.forename: Li-Ying
authors.initials: LY
authors.lastname: Hao
authors.forename: Zahangir A
authors.initials: ZA
authors.lastname: Saud
authors.forename: Jian-Jun
authors.initials: JJ
authors.lastname: Xu
authors.forename: Asako
authors.initials: A
authors.lastname: Kameyama
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Maki
authors.forename: Kirsty K
authors.initials: KK
authors.lastname: Jewell
authors.forename: Tim
authors.initials: T
authors.lastname: Parr
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Bardsley
authors.forename: Masaki
authors.initials: M
authors.lastname: Kameyama
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D066298:In Vitro Techniques; D032383:Myocytes, Cardiac / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D017434:Protein Structure, Tertiary / Q000235:genetics
chemical_list: D020746:Calcium Channels, L-Type; D002135:Calcium-Binding Proteins; C033668:calpastatin