Beyond non-integer Hill coefficients: A novel approach to analyzing binding data, applied to Na+-driven transporters.

RAVERA, S; QUICK, M; NICOLA, JP; CARRASCO, N; AMZEL, LM

ROCKEFELLER UNIV PRESS

Lugar: New York; Año: 2015 vol. 145 p. 555 - 555

rokaryotic and eukaryotic Na(+)-driven transporters couple the movement of one or more Na(+) ions down their electrochemical gradient to the active transport of a variety of solutes. When more than one Na(+) is involved, Na(+)-binding data are usually analyzed using the Hill equation with a non-integer exponent n. The results of this analysis are an overall Kd-like constant equal to the concentration of ligand that produces half saturation and n, a measure of cooperativity. This information is usually insufficient to provide the basis for mechanistic models. In the case of transport using two Na(+) ions, an n < 2 indicates that molecules with only one of the two sites occupied are present at low saturation. Here, we propose a new way of analyzing Na(+)-binding data for the case of two Na(+) ions that, by taking into account binding to individual sites, provides far more information than can be obtained by using the Hill equation with a non-integer coefficient: it yields pairs of po