The unique insert in myosin VI is a structural calcium-calmodulin binding site.
Proc Natl Acad Sci U S A
; 101(14): 4787-92, 2004 Apr 06.
Article
em En
| MEDLINE
| ID: mdl-15037754
ABSTRACT
Myosin VI contains an inserted sequence that is unique among myosin superfamily members and has been suggested to be a determinant of the reverse directionality and unusual motility of the motor. It is thought that each head of a two-headed myosin VI molecule binds one calmodulin (CaM) by means of a single "IQ motif". Using truncations of the myosin VI protein and electrospray ionization(ESI)-MS, we demonstrate that in fact each myosin VI head binds two CaMs. One CaM binds to a conventional IQ motif either with or without calcium and likely plays a regulatory role when calcium binds to its N-terminal lobe. The second CaM binds to a unique insertion between the converter region and IQ motif. This unusual CaM-binding site normally binds CaM with four Ca2+ and can bind only if the C-terminal lobe of CaM is occupied by calcium. Regions of the MD outside of the insert peptide contribute to the Ca(2+)-CaM binding, as truncations that eliminate elements of the MD alter CaM binding and allow calcium dissociation. We suggest that the Ca(2+)-CaM bound to the unique insert represents a structural CaM, and not a calcium sensor or regulatory component of the motor. This structure is likely an integral part of the myosin VI "converter" region and repositions the myosin VI "lever arm" to allow reverse direction (minus-end) motility on actin.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Calmodulina
/
Cálcio
/
Cadeias Pesadas de Miosina
Idioma:
En
Revista:
Proc Natl Acad Sci U S A
Ano de publicação:
2004
Tipo de documento:
Article
País de afiliação:
França