Motor interaction protein

The ribbon is composed mainly of the structural protein, Ribeye, but also includes a kinesin motor protein, KIF3A, and Rab3-interacting protein, RIM. Ribbons are attached to the synaptic active zone by bassoon, and its structural relative, piccolo. Although the ribbon appears to anchor a readily releasable pool of vesicles, molecular motors do not appear to be involved in vesicle movements near the active zone. RDVt protein mutations have been implicated in an autosomal dominant rod-cone dystrophy (Johnson et al., 2003). 

Just as myosins are able to move along microfilaments, there are motor proteins that move along microtubules. Microtubules, like microfilaments, are polar polymeric assemblies, but unlike actin-myosin interactions, microtubule-based motors exist that move along microtubules in either direction. A constant traffic of vesicles and organelles is visible in cultured cells especially using time-lapse photography. The larger part of this movement takes place on micrombules and is stimulated by phorbol ester (an activator of protein kinase C), and over-expression of N-J aj oncoprotein (Alexandrova et al., 1993). 

A neurally derived signaling protein, agrin, acts through a receptor tyrosine kinase, MuSK, in the formation of the specialized postsynaptic endplate by interaction with rapsyn. Thus, MuSK-rapsyn interactions are critical in forming the local scaffold for postsynaptic components in the motor endplate [43,44]. 

The structural hypothesis, which was formulated in response to observations that axonal transport rate components move as discrete waves, each with a characteristic rate and a distinctive composition, can explain the coherent transport of functionally related proteins and is consistent with the relatively small numbers of motor molecules in neurons. The only assumption is that the number of elements that can interact with transport motor complexes is limited, and this requires appropriate packaging of the transported material. Different rate components result from packaging of transported material into different, cytologically identifiable, structures. In fact, the faster rates reflect the transport of proteins preassembled as membranous organelles, including vesicles and... 

The macroscopic rates measured by radiolabel experiments should not be taken to reflect maximum rates of the motors involved. As with mitochondrial transport, the net rate of slow component proteins reflects both the rate of actual movement and the fraction of a time interval that a structure is moving. The elongate shape of cytoskeletal structures and their potential for many interactions means that net displacements are discontinuous. If a structure is moving at a speed of 2 j,m/s, but on average only moves at that rate for one second out of every 100 seconds, then the average rate for the structure will translate to a net rate of only 0.02 pm/s [31]. 

HDAC9 is the predominant member of the class II HDAC family expressed in heart (Zhang et al, 2002). Its major product was shown to encode the splice variant MEF2-interacting transcription repressor/histone deacetylase-related protein (MITRIHDRP), which lacks the enzymatic domain but forms complexes with both HDACI and HDAC3 (Zhou et al, 2000 Zhou et al, 2001) and has been recently implicated in skeletal muscle chromatin acetylation and gene expression under motor innervation control (Mejat et al, 2005). 

Many experiments have been carried out by using this setup the stretching of single DNA molecules, the unfolding of RNA molecules or proteins, and the translocation of molecular motors (Fig. 2). Here we focus our attention on force experiments where mechanical work can be exerted on the molecule and nonequilibrium fluctuations are measured. The most successful studies along this line of research are the stretching of small domain molecules such as RNA [83] or protein motifs [84]. Small RNA domains consist of a few tens of nucleotides folded into a secondary structure that is further stabilized by tertiary interactions. Because an RNA molecule is too small to be manipulated with micron-sized beads, it has to be inserted between molecular handles. These act as polymer spacers that avoid nonspecific interactions between the bead and the molecule as well as the contact between the two beads. 

Protein Interactions Modulated by Chemical Energy Actin, Myosin, and Molecular Motors 182... 

Protein-ligand interactions achieve a special degree of spatial and temporal organization in motor proteins. Muscle contraction results from choreographed interactions between myosin and actin, coupled to the hydrolysis of ATP by myosin. 

In its active form CheA undergoes autophosphorylation, that is, the phosphorylation of a histidine imidazole group in one of its subunits by the protein kinase active site of an adjacent subunit. The phospho group is then transferred from phospho-CheA to another protein, CheY. Phospho-CheY interacts with the flagellar motor proteins (Chapter 19) periodically causing a reversal of direction of the bacterial flagella. As a result the bacteria tumble and then usually move... 

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