The steady-state kinetics of chicken liver fatty acid synthase has been studied over the pH range 5.9-8.6 in 0.1 M potassium phosphate/1 mM EDTA at 25.0 degrees C. The steady-state initial velocity, v, which was determined by measuring the rate of consumption of NADPH spectrophotometrically over a wide range of substrate concentrations, followed the rate law v = (formula; see text), in which Ac...

The affinity label 5'-p-(fluorosulfonyl)benzoyl adenosine modifies rabbit muscle phosphofructokinase to the extent of one group/subunit. Modification appears to occur at a binding site specific for AMP, cyclic AMP, and ADP, i.e. those adenine nucleotides which are activators under conditions where regulatory kinetic behavior is obtained. The consequences of the modification are consistent with ...

Binding of proteins to membranes is often accompanied by titration of ionizable residues and is, therefore, dependent on pH. We present a theoretical treatment and computational approach for predicting absolute, pH-dependent membrane binding free energies. The standard free energy of binding, DeltaG, is defined as -RTln(P(b)/P(f)), where P(b) and P(f) are the amounts of bound and free protein. ...

The structure factor, S(q), is measured for a set of dispersions that consist of liposome vesicles with differing numbers of ionizable surface groups. These systems allow us to probe the dependence of the local structure on the particle bare charge systematically. The height of the nearest neighbor peak in S(q), which is a direct measure of the spatial order of the vesicles, does not increase m...

We propose a simple model for the calculation of pK(a) values of ionizable residues in proteins. It is based on the premise that the pK(a) shift of ionizable residues is linearly correlated to the interaction between a particular residue and the local environment created by the surrounding residues. Despite its simplicity, the model displays good prediction performance. Under the sixfold cross ...

The ionizable amino acid side chains of proteins are usually located at the surface. However, in some proteins an ionizable group is embedded in an apolar internal region. Such buried ionizable groups destabilize the protein and may trigger conformational changes in response to pH variations. Because of the prohibitive energetic cost of transferring a charged group from water to an apolar mediu...

When azide ion reacts with methemoglobin in unbuffered solution the pH of the solution increases. This phenomenon is associated with increases in the pK values of heme-linked ionizable groups on the protein which give rise to an uptake of protons from solution. We have determined as a functional of pH the proton uptake, delta h+, on azide binding to methemoglobin at 20 degrees C. Data for methe...