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Titolo:
Calcium binding to an elastic portion of connectin/titin filaments
Autore:
Tatsumi, R; Maeda, K; Hattori, A; Takahashi, K;
Indirizzi:
Hokkaido Univ, Fac Agr, Dept Anim Sci, Meat Sci Lab,Kita Ku, Sapporo, Hokkaido, Japan Hokkaido Univ Sapporo Hokkaido Japan b,Kita Ku, Sapporo, Hokkaido, Japan
Titolo Testata:
JOURNAL OF MUSCLE RESEARCH AND CELL MOTILITY
fascicolo: 2, volume: 22, anno: 2001,
pagine: 149 - 162
SICI:
0142-4319(2001)22:2<149:CBTAEP>2.0.ZU;2-H
Fonte:
ISI
Lingua:
ENG
Soggetto:
CHICKEN SKELETAL-MUSCLE; MOLECULAR-WEIGHT PROTEINS; IMMUNOELECTRON MICROSCOPY; ALPHA-CONNECTIN; BETA-CONNECTIN; CARDIAC-MUSCLE; MONOCLONAL-ANTIBODIES; 1,200-KDA SUBFRAGMENT; THICK FILAMENTS; STRIATED-MUSCLE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
86
Recensione:
Indirizzi per estratti:
Indirizzo: Tatsumi, R Hokkaido Univ, Fac Agr, Dept Anim Sci, Meat Sci Lab,Kita Ku, Sapporo, Hokkaido, Japan Hokkaido Univ Sapporo Hokkaido Japan Sapporo, Hokkaido, Japan
Citazione:
R. Tatsumi et al., "Calcium binding to an elastic portion of connectin/titin filaments", J MUSCLE R, 22(2), 2001, pp. 149-162

Abstract

alpha -Connectin/titin-1 exists as an elastic filament that links a thick filament with the Z-disk, keeping thick filaments centered within the sarcomere during force generation. We have shown that the connectin filament hasan affinity for calcium ions and its binding site(s) is restricted to the beta -connectin/titin-2 portion. We now report the localization and the characterization of calcium-binding sites on beta -connectin. Purified beta -connectin was digested by trypsin into 1700- and 400-kDa fragments, which were then subjected to fluorescence calcium-binding assays. The 400-kDa fragment possesses calcium-binding activity; the binding constant was 1.0 x 10(7) M-1 and the molar ratio of bound calcium ions to the 400-kDa fragment reached a maximum of 12 at a free calcium ion concentration of approximately 1.0 muM. Antibodies against the 400-kDa fragment formed a sharp dense stripeat the boundary of the A and the I bands, indicating that the calcium-binding domain constitutes the N-terminal region of beta -connectin, that is, the elastic portion of connectin filaments. Furthermore, we estimated the N-terminal location of beta -connectin of various origins (n = 26). Myofibrils were treated with a solution containing 0.1 mM CaCl2 and 70 muM leupeptinto split connectin filaments into beta -connectin and a subfragment, and chain weights of these polypeptides were estimated according to their mobility in 2% polyacrylamide slab gels. The subfragment exhibited a similar chain weight of 1200 +/- 33 kDa (mean +/- SD), while alpha- and beta -connectins were variable in size according to their origin. These results suggest that the apparent length of the 1200-kDa subfragment portion is almost constant in all instances, about 0.34 mum at the slack condition, therefore that the C-terminus of the 1200-kDa subfragment, that is, the N-terminus of the calcium-binding domain, is at the N-2 line region of parent filaments in situ. Because the secondary structure of the 400-kDa fragment was changed by the binding of calcium ions, connectin filaments could be expected to altertheir elasticity during the contraction-relaxation cycle of skeletal muscle.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 14/07/20 alle ore 03:09:40