Molecular Motors: Myosins and Kinesins PDF

Myosins and molecular motors (biological machines that are the essential agents of movement in living organisms.) Sopio Dzneladze 1 Myosin classes Eighteen classes of myosin have been identified in the human genome. Myosin I-XVIII; Skeletal, cardia...

Myosins and molecular motors (biological machines that are the essential agents of movement in living organisms.) Sopio Dzneladze 1 Myosin classes Eighteen classes of myosin have been identified in the human genome. Myosin I-XVIII; Skeletal, cardiac, and smooth muscle myosins are all in Class II; Sopio Dzneladze 2  Myosin I is a low-molecular-mass motor Myosin I protein that is associated with cell membranes. It contains a tail section rich in basic amino acid residues and can associate with anionic phospholipids. There is a tail section domain rich in glycine, proline, and alanine (GPA domain) that facilitates binding to actin. This class of myosins appears to be involved in membrane-membrane interactions and to function in brush boarders of the small intestines. They may also be involved in transport/movement of Golgi-derived vesicles. Sopio Dzneladze 3 Myosin V Myosin V is involved in organelle transport such as synaptic vesicles, melanosomes , vacuoles, and mRNA. It is found in all brain neurons and is required for melanosome transport. Mutations in myosin V are associated with neurological malfunctions and depigmentation , especially of hair. Sopio Dzneladze 4 Elejalde syndrome Elejalde syndrome is characterized by silvery hair and severe dysfunction of the central nervous system. Large granules of melanin are unevenly distributed in the hair shaft, and abnormal melanocyces and melanosomes may be present in fibroblasts. These observations suggest that mechanisms for their movement and distribution might be defective. Sopio Dzneladze 5 Myosin VI Myosin VI is expressed in most cells and tissues. The neck region is extended and contains one calmodulin (IQ motif) binding region per head. It is a dimeric molecule with a coiled tail that has two globular ends (one for each monomer). Defects in the gene for this protein cause hearing problems attributable to defects in movement of the hairs in the inner ear. Sopio Dzneladze 6 Kinesins Kinesins are microtubule-based molecular motors. They do not form filaments like some myosins, but they generate motion by conformational changes on binding and hydrolysis of ATP in a similar manner to myosin actin-based motors. Sopio Dzneladze 7  The motor domains of kinesins are smaller than those of myosins. A major function of this class of motor proteins is to effect movement of intracellular cargo: vesicles, organelles, portions of the mitotic apparatus , chromosomes , mRNA, proteins , and other cellular constituents. https://gfycat.com/aggrav atinghonestavians Sopio Dzneladze 8 Kinesin 1 https://giphy.com/gifs/protein-kinesin-Vg7 11CGH7x55K Sopio Dzneladze 9 Dynein Axonemal dynein - that effect flagella and cilia movement; cytoplasmic Dyneyn - that effect distribution and organization of cytoplasmic structures. Sopio Dzneladze 10 Sopio Dzneladze 11  T. Devlin. Textbook of biochemistry. Pp. 979- 981. Sopio Dzneladze 12