Membranes protein bodies

Figure 4.4 Comparison of oxidase-dependent iron transport in mammals and yeast. In mammals, the plasma glycoprotein cerulpolasmin mediates iron oxidation, facilitating iron export from the cells and delivery to other tissues throughout the body. In yeast, Fet3p, an integral membrane protein mediates iron oxidation, resulting in plasma membrane iron transport through the permease Ftrlp. Reprinted from Askwith and Kaplan, 1998. Copyright (1998), with permission from Elsevier Science.

Esteban-Martin S, Strandberg E, Fuertes G, Ulrich AS, Salgado J (2009) Influence of whole-body dynamics on 15N PISEMA NMR spectra of membrane proteins a theoretical analysis. Biophys J 96 3233-3241... 

Specific membrane components must be delivered to their sites of utilization and not left at inappropriate sites [3]. Synaptic vesicles and other materials needed for neurotransmitter release should go to presynaptic terminals because they serve no function in an axon or cell body. The problem is compounded because many presynaptic terminals are not at the end of an axon. Often, numerous terminals occur sequentially along a single axon, making en passant contacts with multiple targets. Thus, synaptic vesicles cannot merely move to the end of axonal MTs. Targeting of synaptic vesicles thus becomes a more complex problem. Similar complexities arise with membrane proteins destined for the axolemma or a nodal membrane. 

Microbodies (97-101) are spherical organelles (0.1-2.0 pm in diameter) bounded by a single membrane. They possess a granular interior and sometimes crystalline protein body. A specialized type of microbody is the glyoxysome (0.5-1.5 pm) containing enzymes ofthe glyoxy-late cycle. Glyoxysomes are found in the endosperm or cotyledons of oily or fatty seeds. 

Mulugeta S, Gray JM, Notarfrancesco KL, Gonzales LW, Koval M, Feinstein SI, Ballard PL, Fisher AB, Shuman H (2002) Identification of LBM180, a lamellar body limiting membrane protein of alveolar type II cells, as the ABC transporter protein ABC A3. J Biol Chem 277(25) 22147-22155... 

Furuse M, Fujimoto K, Sato N, Hirase T, Tsukita S, and Tsukita S [1996] Overexpression of occludin, a tight junction-associated integral membrane protein, induces the formation of intracellular multilamellar bodies bearing tight junction-like structures. J Cell Sci 109 429-435... 

Based on the knowledge of the endocytotic pathway, it is reasonable to assume that uhiquitination is reversible until the endocytosed membrane proteins such as neurotransmitter receptors are routed to the multivesicular body for lysosomal degradation. 

Figure 8 Ubiquitin and endocytosis. Receptors on the plasma membrane undergo monoubiquitination as a result of ligand (e.g., neurotransmitter). Ubiquitinated receptors bind to proteins called epsins, which in turn interact with adaptor proteins (adaptin) bound to clathrin-coated pits. Ubiquitination also functions to sort the internalized membrane protein into early endosomes, which directs them to degradation by lysosome through the multivesicular body. If ubiquitin from the endocytosed receptors is removed by an UBP, the receptor recycles back to the membrane. Proteasome inhibitors block endocytotic degradation of some proteins such as glutamate receptor subunits indicating a possible role for the proteasome.

Pathogens that have entered the body—e.g., viruses (top)—are taken up by antigen-presenting cells (APCs) and proteolytically degraded (1). The viral fragments produced in this way are then presented on the surfaces of these cells with the help of special membrane proteins (MHC proteins see p. 296) (2). The APCs include B lymphocytes, macrophages, and dendritic cells such as the skin s Langer-hans cells. 

There is also a preliminary report of a P. frutescens cDNA encoding a membrane protein of unknown function (8R6) that promotes anthocyanin uptake into protoplasts and anthocyanin accumulation when overexpressed in A. thaliana transgenics.Within the vacuole of some plants (but not A. thaliana) the anthocyanins may occur in protein containing bodies, termed anthocyanic vacuolar inclusions (AVIs), whose function is as yet unknown but may relate to transport activities. ... 

For secretary proteins, the diluted baculovirus solution is injected into the body cavity of silkworm larvae at the 5-instar stage (teeNotes 15 and 16). For nonsecretary proteins, including intracellular proteins, membrane proteins, and nuclear proteins, the diluted baculovirus solution is injected into silkworm pupae see Note 17). 

Lipid peroxidation is one of the major sources of free-radical mediated injury that directly damages membranes and generates a number of secondary products. In particular, markers of lipid peroxidation have been found to be elevated in brain tissues and body fluids in several neurodegenerative diseases, and the role of lipid peroxidation has been extensively discussed in the context of their pathogenesis. Peroxidation of membrane lipids can have numerous effects, including increased membrane rigidity, decreased activity of membrane-bound enzymes (e.g., sodium pumps), altered activity of membrane receptors, and altered permeability [Anzai et al., 1999 Yehuda et al., 2002], In addition to effects on phospholipids, lipid-initiated radicals can also directly attack membrane proteins and induce lipid-lipid, lipid-protein, and protein-protein cross-linking, all of which obviously have effects on membrane function. 

Hatzopoulos, P., Franz, G., Choy, L. Sung, R.Z. (1990). Interaction of nuclear factors with upstream sequences of a lipid body membrane protein gene from carrot. The Plant Cell 2, 457-67. 

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