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- Title
The two IQ-motifs and Ca<sup>2+</sup>/calmodulin regulate the rat myosin 1d ATPase activity.
- Authors
Köhler, Danny; Struchholz, Sandra; Bähler, Martin
- Abstract
The light chain binding domain of rat myosin 1d consists of two IQ-motifs, both of which bind the light chain calmodulin (CaM). To analyze the Myo1d ATPase activity as a function of the IQ-motifs and Ca2+/CaM binding, we expressed and affinity purified the Myo1d constructs Myo1d-head, Myo1d-IQ1, Myo1d-IQ1.2, Myo1d-IQ2 and Myo1dΔLV-IQ2. IQ1 exhibited a high affinity for CaM both in the absence and presence of free Ca2+. IQ2 had a lower affinity for CaM in the absence of Ca2+ than in the presence of Ca2+. The actin-activated ATPase activity of Myo1d was∼75% inhibited by Ca2+-binding to CaM. This inhibition was observed irrespective of whether IQ1, IQ2 or both IQ1 and IQ2 were fused to the head. Based on the measured Ca2+-dependence, we propose that Ca2+-binding to the C-terminal pair of high affinity sites in CaM inhibits the Myo1d actin-activated ATPase activity. This inhibition was due to a conformational change of the C-terminal lobe of CaM remaining bound to the IQ-motif(s). Interestingly, a similar but Ca2+-independent inhibition of Myo1d actin-activated ATPase activity was observed when IQ2, fused directly to the Myo1d-head, was rotated through 200°by the deletion of two amino acids in the lever armα-helix N-terminal to the IQ-motif.
- Subjects
MYOSIN; GLOBULINS; MUSCLE proteins; CALMODULIN; CALCIUM-binding proteins; AMINO acids; PROTEINS
- Publication
FEBS Journal, 2005, Vol 272, Issue 9, p2189
- ISSN
1742-464X
- Publication type
Article
- DOI
10.1111/j.1742-4658.2005.04642.x