Specificity-determining loop

Hook, S. S., Kemp, B. E. and Means, A. R., 1999, Peptide specificity determinants at P-7 and P-6 enhance the catalytic efficiency of Ca2+/calmodulin-dependent protein kinase I in the absence of activation loop phosphorylation, J Biol Chem, 274, pp 20215—22. 

Active cyclin-dependent protein kinases are thus heterodimers in which the CDK subunit carries the catalytic activity and the other subunit, the cyclin, performs an activating and specificity-determining function. In addition to association of the cyclin, most CDKs require phosphorylation in the activation segment (T loop or activation segment, see Section 7.2.1) for full activation. 

In this section, the systematic search for conical intersections based on the Longuet-Higgins phase-change rule is described. For conciseness sake, we limit the present discussion to Hiickel-type systems only, unless specifically noted otherwise. The first step in the antilysis is the determination of the LH loops containing a conical intersection for the reaction of interest. 

Striking confirmation of the conclusion that the BET area derived from a Type IV isotherm is indeed equal to the specific surface is afforded by a recent study of a mesoporous silica, Gasil I, undertaken by Havard and Wilson. This material, having been extensively characterized, had already been adopted as a standard adsorbent for surface area determination (cf. Section 2.12). The nitrogen isotherm was of Type IV with a well defined hysteresis loop, which closed at a point below saturation (cf. F, in Fig. 3.1). The BET area calculated from it was 290 5 0 9 m g , in excellent agreement with the value 291 m g obtained from the slope of the initial region of the plot (based on silica TK800 as reference cf. p. 93). 

The a/p-barrel structure is one of the largest and most regular of all domain structures, comprising about 250 amino acids. It has so far been found in more than 20 different proteins, with completely different amino acid sequences and different functions. They are all enzymes that are modeled on this common scaffold of eight parallel p strands surrounded by eight a helices. They all have their active sites in very similar positions, at the bottom of a funnel-shaped pocket created by the loops that connect the carboxy end of the p strands with the amino end of the a helices. The specific enzymatic activity is, in each case, determined by the lengths and amino acid sequences of these loop regions which do not contribute to the stability of the fold. 

Alike any other G-protein coupled receptors (GPCRs), mGlu receptors have seven transmembrane helices, also known as the heptahelical domain (Fig. 2). As observed for all GPCRs, the intracellular loops 2 and 3 as well as the C-terminal tail are the key determinants for the interaction with and activation of G-proteins. However, sequence similarity analysis as well as specific structural features make these mGlu receptors different from many other... 

Roux KH, Taylor KA (2007) AIDS virus envelope spike structure. Curr Opin Struct Biol 17 244-252 Sacktor N, Haughey N, Cutler R, Tamara A, Turchan J, Pardo C, Vargas D, Nath A (2004) Novel markers of oxidative stress in actively progressive HIV dementia. J Neuroimmunol 157 176-184 Samson M, LaRosa G, Libert F, Paindavoine P, Detheux M, Vassart G, Parmentier M (1997) The second extraceUular loop of CCR5 is the major determinant of ligand specificity. J Biol Chem 272 24934-24941... 

Samson M, LaRosa G, Libert F, et al. The second extracellular loop of CCR5 is the major determinant of ligand specificity. J Biol Chem 1997 272(40) 24934-24941. 

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