Biomaterial Database

Orientation of spin-labeled nucleotides bound to myosin in glycerinated muscle fibers. 1987

M S Crowder, and R Cooke

Electron paramagnetic resonance (EPR) spectroscopy of paramagnetic derivatives of ATP has been used to probe the angular distribution of myosin in glycerinated muscle fibers. Three nucleotide spin labels have been prepared with the nitroxide free radical moiety attached, via an ester linkage to either: the 2' or 3' positions of the ribose unit of ATP (SL-ATP), the 2' position of 3' deoxy ATP (2'SL-dATP), or the 3' position of 2' deoxy ATP (3'SL-dATP). In muscle fibers, these nucleotides are quickly hydrolyzed to their diphosphate forms. All three diphosphate analogues bind to the nucleotide site of myosin with similar affinities: rabbit psoas fibers, 7 X 10(3)/M; insect flight muscle, 5 X 10(3)/M; and rabbit soleus muscle, 2 X 10(4)/M. Analysis of the spectra showed that the principal z-axis of the nitroxide attached to bound nucleotides was oriented with respect to the filament axis. The principal axes of 3'SL-dADP and 2'SL-dADP appeared to be preferentially aligned at mean angles of 67 degrees +/- 4 degrees and 55 degrees +/- 5 degrees, respectively. The distribution of probes about these angles can be described by Gaussians with widths of 16 degrees +/- 4 degrees and 13 degrees +/- 5 degrees, respectively. The spectrum of bound SL-ADP was a linear combination of the spectra of the two deoxy analogues. These orientations were the same in the three muscle types examined, indicating a high degree of homology in the nucleotide binding site. Applying static strains as high as 0.2 N/mm2 to muscle fibers caused no change in the orientation of myosin-bound, spin-labeled nucleotides. When muscle fibers were stretched to decrease actin and myosin filament overlap, bound SL-ADP produced EPR spectra indicative of probes with a highly disordered angular distribution. Sodium vanadate and SL-ATP caused fiber stiffness to decrease, and the EPR spectrum of the bound analogue indicated an increase in the fraction of disoriented probes with a concomitant decrease in the fraction of oriented probes. These findings indicate that when myosin is bound to actin its nucleotide site is highly oriented relative to the fiber axis, and when this interaction is removed the orientation of the nucleotide site becomes highly disordered.

UI	MeSH Term	Description	Entries
D007313	Insecta	Members of the phylum ARTHROPODA composed or organisms characterized by division into three parts: head, thorax, and abdomen. They are the dominant group of animals on earth with several hundred thousand different kinds. Three orders, HEMIPTERA; DIPTERA; and SIPHONAPTERA; are of medical interest in that they cause disease in humans and animals. (From Borror et al., An Introduction to the Study of Insects, 4th ed, p1).	Insects,Insect
D009126	Muscle Relaxation	That phase of a muscle twitch during which a muscle returns to a resting position.	Muscle Relaxations,Relaxation, Muscle,Relaxations, Muscle
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D009218	Myosins	A diverse superfamily of proteins that function as translocating proteins. They share the common characteristics of being able to bind ACTINS and hydrolyze MgATP. Myosins generally consist of heavy chains which are involved in locomotion, and light chains which are involved in regulation. Within the structure of myosin heavy chain are three domains: the head, the neck and the tail. The head region of the heavy chain contains the actin binding domain and MgATPase domain which provides energy for locomotion. The neck region is involved in binding the light-chains. The tail region provides the anchoring point that maintains the position of the heavy chain. The superfamily of myosins is organized into structural classes based upon the type and arrangement of the subunits they contain.	Myosin ATPase,ATPase, Actin-Activated,ATPase, Actomyosin,ATPase, Myosin,Actin-Activated ATPase,Actomyosin ATPase,Actomyosin Adenosinetriphosphatase,Adenosine Triphosphatase, Myosin,Adenosinetriphosphatase, Actomyosin,Adenosinetriphosphatase, Myosin,Myosin,Myosin Adenosinetriphosphatase,ATPase, Actin Activated,Actin Activated ATPase,Myosin Adenosine Triphosphatase
D011817	Rabbits	A burrowing plant-eating mammal with hind limbs that are longer than its fore limbs. It belongs to the family Leporidae of the order Lagomorpha, and in contrast to hares, possesses 22 instead of 24 pairs of chromosomes.	Belgian Hare,New Zealand Rabbit,New Zealand Rabbits,New Zealand White Rabbit,Rabbit,Rabbit, Domestic,Chinchilla Rabbits,NZW Rabbits,New Zealand White Rabbits,Oryctolagus cuniculus,Chinchilla Rabbit,Domestic Rabbit,Domestic Rabbits,Hare, Belgian,NZW Rabbit,Rabbit, Chinchilla,Rabbit, NZW,Rabbit, New Zealand,Rabbits, Chinchilla,Rabbits, Domestic,Rabbits, NZW,Rabbits, New Zealand,Zealand Rabbit, New,Zealand Rabbits, New,cuniculus, Oryctolagus
D004578	Electron Spin Resonance Spectroscopy	A technique applicable to the wide variety of substances which exhibit paramagnetism because of the magnetic moments of unpaired electrons. The spectra are useful for detection and identification, for determination of electron structure, for study of interactions between molecules, and for measurement of nuclear spins and moments. (From McGraw-Hill Encyclopedia of Science and Technology, 7th edition) Electron nuclear double resonance (ENDOR) spectroscopy is a variant of the technique which can give enhanced resolution. Electron spin resonance analysis can now be used in vivo, including imaging applications such as MAGNETIC RESONANCE IMAGING.	ENDOR,Electron Nuclear Double Resonance,Electron Paramagnetic Resonance,Paramagnetic Resonance,Electron Spin Resonance,Paramagnetic Resonance, Electron,Resonance, Electron Paramagnetic,Resonance, Electron Spin,Resonance, Paramagnetic
D000227	Adenine Nucleotides		Adenine Nucleotide,Adenosine Phosphate,Adenosine Phosphates,Nucleotide, Adenine,Nucleotides, Adenine,Phosphate, Adenosine,Phosphates, Adenosine
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D012518	Sarcomeres	The repeating contractile units of the MYOFIBRIL, delimited by Z bands along its length.	Sarcomere
D013113	Spin Labels	Molecules which contain an atom or a group of atoms exhibiting an unpaired electron spin that can be detected by electron spin resonance spectroscopy and can be bonded to another molecule. (McGraw-Hill Dictionary of Chemical and Technical Terms, 4th ed)	Spin Label,Label, Spin,Labels, Spin