Kinetic mechanism of myosin IXB and the contributions of two class IX-specific regions

Vijayalaxmi Nalavadi, M. Nyitrai, Cristina Bertolini, Nancy Adamek, Michael A. Geeves, Martin Bahler

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

Myosin IXb (Myo9b) was reported to be a single-headed, processive myosin. In its head domain it contains an N-terminal extension and a large loop 2 insertion that are specific for class IX myosins. We characterized the kinetic properties of purified, recombinant rat Myo9b, and we compared them with those of Myo9b mutants that had either the N-terminal extension or the loop 2 insertion deleted. Unlike other processive myosins, Myo9b exhibited a low affinity for ADP, and ADP release was not rate-limiting in the ATPase cycle. Myo9b is the first myosin for which ATP hydrolysis or an isomerization step after ATP binding is rate-limiting. Myo9b-ATP appeared to be in a conformation with a weak affinity for actin as determined by pyrene-actin fluorescence. However, in actin cosedimentation experiments, a subpopulation of Myo9b-ATP bound F-actin with a remarkably high affinity. Deletion of the N-terminal extension reduced actin affinity and increased the rate of nucleotide binding. Deletion of the loop 2 insertion reduced the actin affinity and altered the communication between actin and nucleotide-binding sites.

Original languageEnglish
Pages (from-to)38957-38968
Number of pages12
JournalJournal of Biological Chemistry
Volume280
Issue number47
DOIs
Publication statusPublished - Nov 25 2005

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Actins
Myosins
Kinetics
Adenosine Triphosphate
Adenosine Diphosphate
Nucleotides
Isomerization
myosin IXB
Adenosine Triphosphatases
Conformations
Rats
Hydrolysis
Fluorescence
Binding Sites
Communication
Head
Experiments

ASJC Scopus subject areas

  • Biochemistry

Cite this

Kinetic mechanism of myosin IXB and the contributions of two class IX-specific regions. / Nalavadi, Vijayalaxmi; Nyitrai, M.; Bertolini, Cristina; Adamek, Nancy; Geeves, Michael A.; Bahler, Martin.

In: Journal of Biological Chemistry, Vol. 280, No. 47, 25.11.2005, p. 38957-38968.

Research output: Contribution to journalArticle

Nalavadi, Vijayalaxmi ; Nyitrai, M. ; Bertolini, Cristina ; Adamek, Nancy ; Geeves, Michael A. ; Bahler, Martin. / Kinetic mechanism of myosin IXB and the contributions of two class IX-specific regions. In: Journal of Biological Chemistry. 2005 ; Vol. 280, No. 47. pp. 38957-38968.
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