Complexes heterodimeric

Figure 9.12 Schematic diagram of the structure of the heterodimeric yeast transcription factor Mat a2-Mat al bound to DNA. Both Mat o2 and Mat al are homeodomains containing the helix-turn-helix motif. The first helix in this motif is colored blue and the second, the recognition helix, is red. (a) The assumed structure of the Mat al homeodomain in the absence of DNA, based on Its sequence similarity to other homeodomains of known structure, (b) The structure of the Mat o2 homeodomain. The C-terminal tail (dotted) is flexible in the monomer and has no defined structure, (c) The structure of the Mat a 1-Mat a2-DNA complex. The C-terminal domain of Mat a2 (yellow) folds into an a helix (4) in the complex and interacts with the first two helices of Mat a2, to form a heterodimer that binds to DNA. (Adapted from B.J. Andrews and M.S. Donoviel, Science 270 251-253, 1995.)...

How is the binding specificity of the heterodimer achieved compared with the specificity of Mat a2 alone The crystal structure rules out the simple model that the contacts made between the Mat a2 homeodomain and DNA are altered as a result of heterodimerization. The contacts between the Mat o2 homeodomain and DNA in the heterodimer complex are virtually indistinguishable from those seen in the structure of the Mat o2 monomer bound to DNA. However, there are at least two significant factors that may account for the increased specificity of the heterodimer. First, the Mat al homeodomain makes significant contacts with the DNA, and the heterodimeric complex will therefore bind more tightly to sites that provide the contacts required by both partners. Second, site-directed mutagenesis experiments have shown that the protein-protein interactions involving the... 

The structure of the LH2 complex of R. acidophila is both simple and elegant (Figure 12.17). It is a ring of nine identical units, each containing an a and a P polypeptide of 53 and 41 residues, respectively, which both span the membrane once as a helices (Figure 12.18). The two polypeptides bind a total of three chlorophyll molecules and two carotenoids. The nine heterodimeric units form a hollow cylinder with the a chains forming the inner wall and the P chains the outer wall. The hole in the middle of the cylinder is empty, except for lipid molecules from the membrane. 

Nuclear Receptor Regulation of Hepatic Cytochrome P450 Enzymes. Figure 1 General mechanism for transcriptional activation of CYP genes by xenochemicals that activate their cognate xeno-receptor proteins. In the case of Ah receptor, the receptor s heterodimerization partner is Arnt, whereas in the case of the nuclear receptors CAR, PXR, and PPARa, the heterodimerization partner is RXR. The coactivator and basal transcription factor complexes shown are each comprised of a large number of protein components. 

There has been an extensive search for additional opioid receptor genes with homology to p, 8, and k receptors which was, however, unsuccessfiil. It is likely, therefore, that the functional properties of the subdivision of p, 8, and k receptors as well as that of the e and X receptors results from alternate mRNA processing, posttranslational modification of the receptor, and/ or from the formation of homo- and heterodimeric receptor complexes. 

Cytokine receptors that couple to the JAK-STAT Pathway decode the signaling though hematopoietic cytokines (erythropoietin, thrombopoietin, colony-stimulating factors), prolactin, growth hormone, the a-, (3- and y- interferons, and a number of immunomodulatory interleukins [3], They form homodimetic or heterodimeric receptor complexes, which after ligandbinding recruit and activate isotypes of Janus kinases (JAKs). Activated JAKs in turn... 

McGraw DW, Mihlbachler KA, Schwarb MR, et al. Airway smooth muscle prostaglandin-EPl receptors directly modulate beta2-adrenergic receptors within a unique heterodimeric complex. J Clin Invest 2006 116 1400-1409. 

Strandberg E, Tremouilhac P, Wadhwani P, Ulrich AS (2009) Synergistic transmembrane insertion of the heterodimeric PGLa/magainin 2 complex studied by solid-state NMR. BBA-Biomembranes 1788 1667-1679... 

Application of the SCM method to the opioid receptor subtypes (187,188) supported the experimental evidence of subtype specificity in the process of heterodimerization of these receptors (96). Although likely heterodimerization interfaces of the 5-p and 5-k opioid receptor complexes were predicted using the SCM method, the application of this procedure to explore the putative interface between p and k opioid receptors resulted in a null set for residues that indicates the absence of a predicted dimerization interface. This result is in full agreement with previous experimental observations (96). 

Svensson, S., Oestberg, T., Jacobsson, M., Norstroem, C., Stefansson, K., Hallen, D., Johansson, I.C., Zachrisson, K., Ogg, D. and Jendeberg, L. (2003) Crystal structure of the heterodimeric complex of LXRa and RXRP ligand-binding domains in a fully agonistic conformation. The EM BO Journal, 22, 4625-4633. 

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