A troponin switch that regulates muscle contraction by stretch instead of calcium.
EMBO J
; 23(4): 772-9, 2004 Feb 25.
Article
em En
| MEDLINE
| ID: mdl-14765112
ABSTRACT
The flight muscles of many insects have a form of regulation enabling them to contract at high frequencies. The muscles are activated by periodic stretches at low Ca2+ levels. The same muscles also give isometric contractions in response to higher Ca2+. We show that the two activities are controlled by different isoforms of TnC (F1 and F2) within single myofibrils. F1 binds one Ca2+ with high affinity in the C-terminal domain and F2 binds one Ca2+ in the C-terminal domain and one exchangeable Ca2+ in the N-terminal domain. We have characterised the isoforms and determined their effect on the development of stretch-activated and Ca2+-activated tension by replacing endogenous TnC in Lethocerus flight muscle fibres with recombinant isoforms. Fibres with F1 gave stretch-activated tension and minimal isometric tension; those with F2 gave Ca2+-dependent isometric tension and minimal stretch-activated tension. Regulation by a TnC responding to stretch rather than Ca2+ is unprecedented and has resulted in the ability of insect flight muscle to perform oscillatory work at low Ca2+ concentrations, a property to which a large number of flying insects owe their evolutionary success.
Texto completo:
1
Bases de dados:
MEDLINE
Assunto principal:
Cálcio
/
Troponina C
/
Heterópteros
/
Miofibrilas
Limite:
Animals
Idioma:
En
Revista:
EMBO J
Ano de publicação:
2004
Tipo de documento:
Article
País de afiliação:
Alemanha