Conformational motility

An interesting parallel was drawn between the N -> / equilibrium and the open-crevice-closed-crevice equilibrium of cytochrome c. Spectroscopic evidence had indicated that the heme iron was buried in a crevice and to account for its reactivity with ligands, conformational motility was proposed between a nonreactive closed... 

In addition to its effects on enzymes and ion transport, Ca /calmodulin regulates the activity of many structural elements in cells. These include the actin-myosin complex of smooth muscle, which is under (3-adrenergic control, and various microfilament-medi-ated processes in noncontractile cells, including cell motility, cell conformation changes, mitosis, granule release, and endocytosis. 

Tomishige, M., and Vale, R. D. (2000). Controlling kinesin by reversible disulfide cross-linking Identifying the motility-producing conformational change./. Cell Biol. 151, 1081-1092. 

Cell Biol. 28, 1185-1189, 1996 Szymanski, P.T., Calponin (CaP) as a latch-bridge protein — a new concept in regulation of contractility in smooth muscle, J. Muscle Res. Cell Motil. 25,7-19,2004 Lehman, W., Craig, R., Kendrick-Jones, J., and Sulherland-Smith, A.J., An open or closed case for the conformation of calponin homology domains on F-actin J. Muscle Res. Cell Motil. 25, 351-358, 2004 Feijani, L, Fattoum, A., Maciver, S.K. et al., A direct interaction with calponin inhibits the actin-nucleating activity of gelsohn, Biochem. J. 396, 461 68, 2006. 

Conformational Fluctuation of Actin and Activation of Myosin Motility... 

Actin filaments are the tracks for myosin movement. Biochemically, actin activates the ATP hydrolysis of myosin. Recently, it has been shown that myosin motility is activated through actin conformational changes. Singlemolecule FRET from doubly labeled actin monomers in the filament has revealed that actin has multiple conformations and spontaneously changes between them with time (Fig. 12.4a, b) [34]. The multiple conformations are... 

FIGURE 3 Conformation and relative activity of dephosphorylated folded monomers, dephosphorylated filaments, and phos-phorylated filaments. Reprinted from Trybus, K. Cell Motility and the Cytoskeleton 18, Copyright 1991 Wiley-Liss, a subsidiary of John Wiley and Sons, Inc. 

Proteins, with a specific function and isolated from a single source, usually have a homogeneous population of molecules all with the same unique amino acid sequence. Yet with 20 different amino acids possible at each position in a polypeptide chain of n residues, 20 different primary structures are theoretically possible. Furthermore, the great majority of all molecules of a natural protein may exist in a unique conformation despite the degrees of freedom formally permitted by rotation about the peptide backbone (motility) and side chains (mobility). For example, with only 3 conformations defined per residue, a polypeptide chain of 210 residues would have a theoretical possibility of existing in 10 °° different conformations. 

The coenzyme could modify the motility of the enzyme molecule by stabilizing some conformational forms which would be favored over the others, with consequent modifications of the rate and extent of hydrogen exchange. Motility indicates continuous structural changes in parts of the protein molecule (Linderstiam-Lang and Schellman, 1959). 

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