Quaternary complex

Now ku < 0.8 X 109 sec.-1, only slightly smaller than the upper limit 9 < 1.1 X 109 sec.-1 Apparently the unimolecular dissociation rate constants of all secondary complexes are less than ca. 5 X 107 sec.-1, those of the tertiary complexes less than 109 sec.-1, and those of the quaternary complexes probably of the order of 1010 sec.-1 These conclusions substantiate the view 16) that the mass spectrometrically observed tertiary ions arise predominantly from dissociation of the intermediate addition complexes C6Hi2+, C6Hn+, and C6Hi0+. Higher order ions, however, should arise principally from reactions of the dissociation products of the above complexes 62). 

Figure 6.7. Phosphatidylinositol 4,5-bisphosphate hydrolysis by phospholipase C. Occupancy of receptors (R) results in exchange of bound GDP for GTP on the a-subunit of a het-erotrimeric G-protein. The a-subunit then dissociates from the fi- and y-subunits and activates phospholipase (PLC). This enzyme is calcium dependent and, upon activation, can hydrolyse phosphatidylinositol 4,5-bisphosphate (PIP2). The products of this hydrolysis are inositol 1,4,5-trisphosphate (Ins 1,4,5-P3), which is released into the cytoplasm, and diacylglycerol (DAG), which remains in the membrane. The DAG is an activator of protein kinase C, which moves from the cytoplasm to the membrane, where it forms a quaternary complex with DAG and Ca2+. 

Or (right) another transcription factor (shown in grey) is recruited to its binding site (yellow) forming a quaternary complex which might either be stable or lead to loss of HMG81,... 

The kinetic reaction mechanism appears to be random, and for the reaction to proceed, all substrates must reside as a E-D-Ala-D-Ala-MgATP quaternary complex. Except for its activation of an a-carboxylate to form a peptide bond, the enzyme s mechanism appears to be completely analogous to that catalyzed by glutamine synthetase, which forms a y-glutamyl-phosphate intermediate. There is strong evidence for the participation... 

Any binary, ternary, or quaternary complex formed upon the association of a substrate with the free enzyme or other enzyme form such a complex is often called the Michaelis complex. 

Complexes formed from the ordered or random combination of four distinct entities. Many three-substrate enzymes proceed via the formation of a reversible E-A-B-C quaternary complex. 

Fig. 5.2. Methods for detection of passenger-ligand interaction. (A) Fluorophore-coupled ligand (B) fluorophore-coupled antibody (C) quaternary complex generated by subsequent rounds of incubation with ligand, primary antibody, biotinylated second antibody, and strep ta-vidin, R-phycoerythrin conjugate (D) quaternary complex generated by subsequent rounds of incubation wi tli ligand, primary antibody, biotinylated second antibody, and streptavidin-coated magnetobeads. L ligand P passenger.

Benfenati F, Valtorta F, Rubenstein JL et al (1992b) Synaptic vesicle-associated Ca2+/calmodulin-dependent protein kinase II is a binding protein for synapsin I. Nature 359 417-20 Benians A, Nobles M, Hosny S et al (2005) Regulators of G-protein signaling form a quaternary complex with the agonist, receptor, and G-protein. A novel explanation for the acceleration of signaling activation kinetics. J Biol Chem 280 13383-94... 

Simple binary interactions were not enough to achieve a long-term stability [24, 25]. Table 6 presents relative stabilities of binary and quaternary complex structures. This table qualitatively illustrates the concept that multiple interactions are necessary in order to stabilize the final product. Both binary and some ternary interactions in Table 7 showed instability throughout the matrix. This behavior was very common. Matrix stability was normally evaluated in 0.9 % NaCl or PBS (phosphate-buffered saline), fluids of physiologic significance. The introduction of more ingredients into the nanoparticulate formulation also increased... 

Rapid attack of the chelator to give a quaternary complex. 

The three-dimensional structure of the DNA-binding domains of NF-AT, Fos, and Jun in a quaternary complex with a DNA fi agment from the IL-2 gene promoter provides an explanation why more than one transcriptional regulator is necessary to give a productive... 

The structural and spectroscopic studies provide a firm foundation upon which to postulate a catalytic mechanism, but unfortunately give little insight into the activation of dioxygen within the reactive quaternary complex. Two key intermediates are presented in Figure 18. The first is an adduct of the coordinatively unsaturated iron(II) center, O2 and the nearby C4a of the BH4 cofactor, which is best described as an iron(II)-peroxypterin complex (Figure Since no intermediate has been directly... 

T. Lagrange, et al. High-resolution mapping of nucleoprotein complexes by site-specific protein-DNA photocrosslinking organization of the human TBP-TFUA- TFUB-DNA quaternary complex. Proc. Nad. Acad. Sci. USA 93 (1996) 10620-5. 

In mammals Fatty Acid Synthase (FAS) catalyzes fatty acid synthesis on a homodimeric enzyme, each monomer of which has seven catalytic activities, and eight sites (In bacteria such as E. colt there are seven separate enzymes plus an acyl-carrier protein. Plants also have individual proteins for the various activities which are associated in a quaternary complex. In eukaryotes other than plants the FAS are complexes of multifunctional proteins. The enzyme weighs approximately 500,000 Daltons. 

Several reports have appeared of the syntheses and structures of mixed-ligand quaternary complexes involving terpy, [Yb(acac)(terpy)(N03)2], [Nd(hfac)(terpy)(N03)2(H20)], ... 

Most kinetic studies of iron release have focused on pathways involving the use of chelate ligands such as EDTA (217), pyrophosphate 218-220), phosphonates 220,221), catecholates 108,216), hydroxa-mates 120), and nitrilotriacetate (221). In many cases, simple saturation kinetics are observed, and interpreted in terms of the formation of a quaternary complex, ligand-Fe-transferrin-COs (120,122). The failure to observe this complex spectroscopically [in contrast to iron uptake studies (120)] has been explained in terms of a rate-limiting conformational change, giving a basic three-step mechanism, which is essentially the reverse of that given for iron uptake (Section V.A.l). 

For example, the approximate ratios useful for transfection in a report using this particular quaternary complex are 2 x 1010 adenoviral particles 1.25 pg antibody-polylysine complex 6 pg plasmid DNA, added to 6 pg polylysine or 8 pg polylysine-transferrin complex (74). Simple mixing of the components results tin rapid and spontaneous formation of the macrocomplex. Carbohydrates have also been used as targeting ligands (84,85). 

Entelis assumes the formation of an activated alcohol-isocyanate binary complex during the catalysis of the methanol-phenyl isocyanate reaction by dibutyltin dilaurate (DBTDL) (3, 5) Activated alcohol-isocyanate-catalyst ternary complexes have also been proposed by others. However, significant differences can be noted in the structures of either the postulated one (2, 4, 6, 7) or two (8) coordination positions of the isocyanate to the metal. To explain the synergistic effects observed when tertiary amine and organometallic compounds are combined, several authors suggest the formation of an activated quaternary complex I, II or III (2, 6, 9, 10, 11, 27). 

On the basis of these results, the polyurethane catalysis by organometallic compounds can hardly be explained by an activated binary complex as proposed by Entelis. Ternary or quaternary complexes are more realistic catalytic pathways but their present description is not necessarily the best one (16). All the complexation possibilities are not taken into account. 

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