Chi a/b binding proteins

A family of Chi a/b binding proteins are found in green plants.308 These have apparently evolved inde-... 

B. The Minor Chi a/b Binding Protein Complexes CP29, CP26 and CP24.216... 

The minor Chi a/b binding proteins, namely CP29, CP26 and CP24., which occupy an intermediate position between the core antennas of (1) above and the peripheral antenna in (3) below. 

The outermost Chi a/b binding proteins, called LHC II (light-harvesting complex associated with photosystem II). 

In the present analysis we apply the excitonic approach to the CP29 complex, one of the three minor chlorophyll a/b (Chi a/b)-binding proteins associated with the photosystems II in plants and algae. CP29 is a... 

In this report experimental evidence is presented for a new Chi a/b binding protein in purified PS II membrane fragments with a relative molecular mass of 14-15 kDa. It has been isolated and characterized by biochemical, spectroscopic and immunological means. A possible functional role of this new component within PSII is discussed. 

Although major progresses have been recently made, still some basic features of the structural and molecular organization of chi a/b binding proteins such as polypeptide and pigment composition are not well defined. In this study we describe the use of improved analytical methods for the isolation and characterization of chlorophyll-proteins. Their use offers new possibilities to investigate the organization of the PSII antenna system. 

The three minor types of Chl-a/b binding proteins are somewhat more distant from the reaction center, with CP29 and CP26 slightly closer to the reaction center than CP24, as determined by freeze-etch EM experiments and as indicated in Fig. 1 (B). Each of the three minor Chi a/b complexes binds... 

Table III relative protein content (%) of chi a/b binding polypeptides in sucrose gradient bands 2, 3 and 4 containing chlorophyll a/b proteins) from DM solubilized PSII membranes.

Survival of the Mn-binding site(s) in the CaClo-treated PS n membranes was assayed as described (2). Binding of light-harvesting Chi a/b protein (LHC) to Mn was examined by an equilibrium dialysis. LHCs were isolated from CaCl2-treated PS n membranes by centrifugation (224,000 x g, 4 hr) in the presence of 60 mM octylglucoside. After the... 

FIGURE 3. Model of PS II, surface view. "47 =CPa-l, reaction centre complex carrying P680 43"= CPa-2, Chi a antenna 29"=CP 29, Chi a+b antenna "34"=34 kd herbicide-binding protein with secondary acceptor "B LHC"=... 

The structure of the major trimeric LHCII complex has been recently obtained at 2.72 A (Figure 7.3) (Liu et al., 2004). It was revealed that each 25kDa protein monomer contains three transmembrane and three amphiphilic a-helixes. In addition, each monomer binds 14 chlorophyll (8 Chi a and 6 Chi b) and 4 xanthophyll molecules 1 neoxanthin, 2 luteins, and 1 violaxanthin. The first three xanthophylls are situated close to the integral helixes and are tightly bound to some amino acids by hydrogen bonds to hydroxyl oxygen atoms and van der Waals interactions to chlorophylls, and hydrophobic amino acids such as tryptophan and phenylalanine. 

Etanercept is a dimeric fusion protein composed of human IgGl constant regions (Ch2, Ch3, and hinge, not ChI) fused to the TNF receptor. Etanercept binds to both TNF- and TNF-B and appears to have effects similar to that of infliximab, ie, inhibition of TNF- -mediated inflammation, but its half-life is shorter due to its physical form (fusion protein) and the route of injection... 

The polypeptides of the light-harvesting complex are most easily resolved by polyacrylamide gel electrophoresis of thylakoid membranes solubilized with sodium or lithium dodecyl sulphate. This produces the green chlorophyll-protein band, CP II, which on staining for protein reveals up to four polypeptides of 24-27 kDa [2], each of which is believed to bind Chi a and Chi b. In most plants two polypeptides predominate, but other minor polypeptides may be resolved [2]. 

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