Lipid-binding proteins cytoplasmic

As-p18, the First Secreted Cytoplasmic Lipid-binding Protein... 

Martenson, R. and Uyemura, K. Myelin P2, a neuritogenic member of the family of cytoplasmic lipid binding proteins. In R. E. Martenson (ed.), Myelin biology and chemistry. Boca Raton, FL CRC Press, 1992, pp. 509-530. 

Basic protein P2 has a molecular weight of 15 kDa and is a member of a family of cytoplasmic lipid-binding proteins. Unlike other myelin proteins, its quantitative expression varies greatly according to species, ranging from less than 1% in rodent sciatic nerves up to 5-14% in human, bovine, and rabbit nerve. P2 is located on the cytoplasmic side of compacted regions of myelin. 

Veerkamp, J.H., and R.G.H.J. Maatman (1995). Cytoplasmic fatty acid binding proteins their structure and genes. Prog. Lipid Res. 34 17-52. Viru, A. (1994). Molecular cellular mechanisms of training effects. J. Sports Med. Phys. Fitness 34 309-322. 

Although none of the G-protein subunits contains regions that might obviously associate with a lipid bilayer, heterotrimeric G-proteins are associated with the cytoplasmic surface of the plasma membrane as is Ras p21 and some of the other low molecular weight GTP-binding proteins. This is apparendy due to the fact that the y-subunits of the heterotrimeric G-proteins are prenylated, as is ras, and at least some of the G-protein a-subunits, e.g. Gj subfamily. 

Outline of the cellular events that result in the activation of protein kinase C (PKC). The enzyme apparently exists in at least two states. Recent sequence work indicates that it has a Ca -binding site of the EF-hand type. When no Ca " ion is bound, and when the concentration of diacylglycerol (DG) in the inner layer of the plasma membrane is low, the kinase exists in a low-activity form, possibly dissociated from the membrane. When a hormone binds to a plasma-membrane receptor (R), cleavage of phosphoinositol into 1,4,5-1P3 and DG is induced. The latter lipid may bind to and activate the calcium-loaded form of PKC. The active form of protein kinase C will now phosphorylate other cytoplasmic proteins, and in this way modify their biochemical properties. R = receptor PL-C = phospholipase C G = a GTP-binding protein that is assumed to act as an intermediary between the receptor and the membrane bound PL-C. 

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