Probing cross-bridge angular transitions using multiple extrinsic reporter groups

Journal Article · Tue Jan 14 00:00:00 EST 1992 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00116a030· OSTI ID:5560035

Ajtai, K; Ringler, A; Burghardt, T P ^[1]

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1. Mayo Foundation, Rochester, MN (United States)

{sup 15}N- and {sup 2}H-substituted maleimido- TEMPO spin label (({sup 15}N, {sup 2}H)MTSL) and the fluorescent label 1,5-IAEDANS were used to specifically modify sulfhydryl 1 of myosin to study the orientation of myosin cross-bridges in skeletal muscle fibers. The electron paramagnetic resonance (EPR) spectrum from muscle fibers decorated with labeled myosin subfragment 1 (({sup 15}N, {sup 2}H)MTSL-S1) or the fluorescence polarization spectrum from fibers directly labeled with 1,5-IAEDANS was measured from fibers in various physiological conditions. The EPR spectra from fibers with the fiber axis oriented at 90{degree} to the Zeeman field show a clear spectral shift from the rigor spectrum when the myosin cross-bridge binds MgADP. The EPR data from ({sup 15}N,{sup 2}H)MTSL-S1 decorating fibers are combined with the fluorescence polarization data from the 1,5-IAEDANS-labeled fibers to map the global angular transition of the labeled cross-bridges due to nucleotide binding by an analytical method described in the accompanying paper. The authors find that the spin and fluorescent probes are quantitatively consistent in the finding that the actin-bound cross-bridge rotates through a large angle upon binding MgADP. They also find that, if the shape of the cross-bridge is described as an ellipsoid with two equivalent minor axes, then cross-bridge rotation takes place mainly about an axis parallel to the major axis of the ellipsoid. This type of rotation may imitate the rotational motion of cross-bridges during force generation.

• OSTI ID: 5560035
• Journal Information: Biochemistry; (United States), Vol. 31:1; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
MUSCLES
ORIENTATION
MYOSIN
ELECTRON SPIN RESONANCE
DEUTERIUM COMPOUNDS
ELECTRON SPECTRA
IMIDES
MOLECULAR STRUCTURE
NITROGEN 15
GLOBULINS
HYDROGEN COMPOUNDS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PROTEINS
RESONANCE
SPECTRA
STABLE ISOTOPES
550201* - Biochemistry- Tracer Techniques