Does the tenary complex act as a secondary proton pump and a GTP synthase?

It has been suggested that G protein-coupled receptors can act as proton transporters, with the activated G protein-coupled receptor transporting

Automated proton titrations of pancreatic phospholipase A2

A computer-controlled titration system has been developed, tested, and used for analysis of the proton-titration behavior of pancreatic phospholipase A2 from ox, horse, and pig. The results revealed an error in the reported amino acid composition of the equine enzyme. A simple interface for the input of digitized data from a pH meter is described together with the software developed for controlling the titration experiments

Microcomputer interface for computer-controlled enzyme kinetic studies with the monolayer technique

Abstract A microcomputer interface for computer-assisted monolayer experiments was developed, tested, and used for analysis of the enzymatic hydrolysis by pancreatic phospholipases A2 (EC 3.1.1.4) of 1,2-didodecanoyl-sn-glycero-3-sulfate monitored under constant surface pressure. The interface described multiplexes two different analog signals onto one set of 12 data input lines to the computer. One signal is obtained from an electromicrobalance which measures surface pressure of a monomolecular substrate layer in a two-compartment trough. The second signal comes from a 10-turns precision potentiometer which measures the position of a surface barrier. Both signals together determine a velocity value which is output via four data lines to a DC motor that drives the barrier. Software developed specifically to drive the interface, to store data, and to keep pressure constant is describe

A three-dimensional protein model for human cytochrome P450 2D6 based on the crystal structures of P450 101, P450 102, and P450 108.

Cytochromes P450 (P450s) constitute a superfamily of phase I enzymes capable of oxidizing and reducing various substrates. P450 2D6 is a polymorphic enzyme, which is absent in 5-9% of the Caucasian population as a result of a recessive inheritance of gene mutations. This deficiency leads to impaired metabolism of a variety of drugs. All drugs metabolized by P450 2D6 contain a basic nitrogen atom, and a flat hydrophobic region coplanar to the oxidation site which is either 5 or 7 Å away from the basic nitrogen atom. The aim of this study was to build a three-dimensional structure for the protein and more specifically for the active site of P450 2D6 in order to determine the amino acid residues possibly responsible for binding and/or catalytic activity. Furthermore, the structural features of the active site can be implemented into the existing small molecule substrate model, thus enhancing its predictive value with respect to possible metabolism by P450 2D6. As no crystal structures are yet available for membrane-bound P450s (such as P450 2D6), the crystal structures of bacterial (soluble) P450 101 (P450(cam)), P450 102 (P450(BM3)), and P450 108 (P450(terp)) have been used to build a three-dimensional model for P450 2D6 with molecular modeling techniques. Several important P450 2D6 substrates were consecutively docked into the active site of the protein model. The energy optimized positions of the substrates in the protein agreed well with the original relative positions of the substrates within the substrate model. This confirms the usefulness of small molecule models in the absence of structural protein data. Furthermore, the derived protein model indicates new leads for experimental validation and extension of the substrate model