Protein complexes characteristics

Cell junctions protein complexes characteristic for the epithelium which enable contact between adjoining cells or the cell and extracellular matrix. 

In vivo, one of the main groups of carotenoids are the snlfates of eritoxanthin sulfate and of the caloxanthin sulfates. The sulfates of carotenoids are not associated with pigment-protein complexes, for example, they are neither part of the fight harvesting complexes nor of the reaction centers. In nonphotosynthetic bacteria, carotenoids appear sporadically and when present, they have unique characteristics. Some Staphylococci accumulate C30 carotenoids, flavobacteria C45 and C50, while some mycobacteria accumulate C40 carotenoid glycosides. ... 

Specific carotenoid-protein complexes have been reported in plants and invertebrates (cyanobacteria, crustaceans, silkworms, etc.), while data on the existence of carotenoproteins in vertebrates are more limited. As alternatives for their water solubilization, carotenoids could use small cytosolic carrier vesicles." Carotenoids can also be present in very fine physical dispersions (or crystalline aggregates) in aqueous media of oranges, tomatoes, and carrots. Thus these physicochemical characteristics of carotenoids as well as those of other pigments are important issues for the understanding of their bioavailability. 

Six of the CSN subunits contain PCI (proteasome, COP9 signalosome, initiation factor 3) domains and two contain MPN (Mpr-Padl-JV-terminal) domains [58]. These two characteristic domains have been found in three protein complexes the CSN, the 26S proteasome lid complex (lid) and the eIF3 complex. The two domains are composed of about 150 to 200 amino acids at the N- or C-terminus of the CSN subunits. Apparently, the PCI domain has been shown to be important for interactions between CSN subunits. Thus, it might have a scaffolding function [22, 59). 

A second group of electron carriers in mitochondrial membranes are the iron-sulfur [Fe-S] clusters which are also bound to proteins. Iron-sulfur proteins release Fe3+ or Fe2+ plus H2S when acidified. The "inorganic clusters" bound into the proteins have characteristic compositions such as Fe2S2 and Fe4S4. The sulfur atoms of the clusters can be regarded as sulfide ions bound to the iron ions. The iron atoms are also attached to other sulfur atoms from cysteine side chains from the proteins. The Fe-S proteins are often tightly associated with other components of the electron transport chain. For example, the flavoproteins Flavin 1, Flavin 2, and Flavin 3 shown in Fig. 10-5 all contain Fe-S clusters as does the Q-cytochrome b complex. All of these Fe-S clusters seem to be one-electron carriers. 

Specific DNA-protein interactions which either promote or inhibit CT processes through the protein-DNA interface would be the most crucial part of a biological system sensing DNA damage. Recent experiments have shown clearly that DNA-mediated CT processes are modulated both negatively and positively by DNA-binding proteins. Most importantly, each of the observed influences of the proteins can be explained by special structural features of the corresponding DNA-protein complexes. Thus, special DNA-protein interactions result in a characteristic modulation of the DNA-mediated CT. 

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