The structural basis of the cross-bridge cycle

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Presentation transcript:

The structural basis of the cross-bridge cycle

was the first em reconstruction Moore, Huxley, and DeRosier DECORATED ACTIN was the first em reconstruction Moore, Huxley, and DeRosier 1970 J. Mol Biol.

Reconstruction by filtered least squares

Projection every 1° (181 projections) Number of observational equations is 161 x 181=29141 Order of normal matrix 17645. Problem should be well determined

Oops!!

Case 2. Projection every 3°, not enough data to invert the normal matrix. How much data is there? To determine the rank of a positive (semi) definite matrix we determine its eigenvalue spectrum

Decorated actin at 13Å resolving power calculated by filtered least squares

Electron cryo-microscopy (of decorated actin) shows how strong binding of myosin to actin releases nucleotide Holmes, Angert, Kull, Jahn, Schroeder (2003) Nature 425, 423-427

Four sub-domain refinement

The cross-bridge cycle As revealed by crystallography

The molecular mechanism of muscle contraction Geeves, M.A. & Holmes, K.C. (2005) The molecular mechanism of muscle contraction Adv Protein Chem 71, 161-93

Lymn & Taylor, 1971

It must bind to actin strongly or weakly The myosin motor domain must move the lever arm from pre- to post- power stroke. It must bind to actin strongly or weakly Both functions are controlled by ATP binding and hydrolysis

Crystallography on the motor domain (particularly Dictyostelium Myosin 2) shows two conformations of myosin: lever UP and lever DOWN

Diskussionsthemen Nennen Sie die Hauptthesen, über die Sie sprechen werden.

Thema 1 Details über das Thema Argumente und Beispiele Warum ist das Thema für Ihr Publikum von Bedeutung?

switch 1

Fischer et al (2005) PNAS102 6873-8

Fischer et al (2005) PNAS102 6873-8

Weak and Strong Binding

Fig 27

Coureux, P. D. Wells, A. L. Menetrey, J. Yengo, C. M. Morris, C. A Coureux, P. D.Wells, A. L.Menetrey, J.Yengo, C. M.Morris, C. A.Sweeney, H. L.Houdusse, A. (2003) A structural state of the myosin V motor without bound nucleotide Nature 425 419-23

Rayment_chicken

Upper/lower 50K fitted

Myo 5

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