CHEM 361B CHEM MOLECULAR-ARCHITECTURE-IN-MUSCLE-CONTRACTILE-A_2005_ADVANCES-IN-PROTEIN-STUDY GUIDE CHEM

CHEM 361B CHEM MOLECULAR-
ARCHITECTURE-IN-MUSCLE-CONTRACTILE-
A_2005_ADVANCES-IN-PROTEIN-STUDY GUIDE
CHEM


MOLECULAR ARCHITECTURE IN MUSCLE
CONTRACTILE ASSEMBLIES


*Biological Structure and Function
Section, Biomedical Sciences
Division,



Introduction 17
I. Hierarchy..........................................................19
A. Components and Organization of the Sarcomere
..................... 23
B. Actin Filaments . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.......................... 29
C. Vertebrate A‐Band Lattices . . . . . . . . . . . . . . . . . . .
........................ 30
D. The Sliding Filament Model and the


CHEM 361B CHEM MOLECULAR-
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Crossbridge Cycle . . . . . . . . . . . . . . . 31
II. Actin Filament Structure and the Z‐Band........34
A. The Actin Monomer . . . . . . . . . . . . . . . . . . . . . . . .
......................... 34
B. F‐Actin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
........................... 36
C. The Thin Filament and Troponin . . . . . . . . . . . .
........................ 38
D. Filament Organization in the Contractile
Units of Different
Muscle Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
......................... 40
E. The Z‐Band. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.......................... 42
F. Filament Organization in the Vertebrate I‐
Band . . . . . . . . . . . . . . . . . . . . . . 49
III. Myosin Filament Structure and the M‐Band...51
A. The X‐Ray Diffraction Approach to Myosin

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Filament Structure . . . . . . . . 51
B. Myosin Head Organization in Relaxed
Vertebrate Myosin Filaments . . . 56
C. Further A‐Band Analysis: C‐Protein, Titin, and
the Vertebrate M‐Band...............................61
D. Invertebrate Myosin Filaments . . . . . . . . . . . . . . .
......................... 71
E. Crossbridge Arrangements on Different Myosin
Filaments:
Variations on a Theme . . . . . . . . . . . . . . . . . . . . . . . .
....................... 74
F. Conclusion: Implications about the Crossbridge
Mechanism. . . . . . . . . . . 77
References............................................................79



I. IntrodUCTION

The pioneering days of molecular biology in the


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1950s and 1960s saw the determination of a variety
of unknown molecular structures using an array of
then novel techniques. The double helix of DNA was
solved using high‐angle X‐ray fiber diffraction data
(Watson and Crick, 1953; Wilkins et al., 1953). The
technique of protein crystallography came of age
when structures of key globular proteins were
determined for the first time (Kendrew, 1963;
Muirhead and Perutz, 1963). At the same time,
electron microscopy and low‐angle X‐ray fiber
diffraction helped to define the




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