Crystal structures of an Extracytoplasmic Solute Receptor from a TRAP transporter in its open and closed forms reveal a helix-swapped dimer requiring a cation for α-keto acid binding-0

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Taken from "Crystal structures of an Extracytoplasmic Solute Receptor from a TRAP transporter in its open and closed forms reveal a helix-swapped dimer requiring a cation for α-keto acid binding"

BMC Structural Biology 2007;7():11-11.

Published online 15 Mar 2007

PMCID:PMC1839085.

n of binding sites (monomeric unit) was 50 nM. The solid line is a fit with the equation given in the text, yielding K≈ 270 nM. The dashed line is a numerical simulation of a (slightly) cooperative model, assuming that the first binding event occurs with K(1) = 270 nM and the second one with Kd(2) = 0.75 × Kd(1). When fitted by a Hill equation, this model corresponds to a Hill number n ≈ 1.1. Any larger cooperativity would increase the sigmoidal character of the binding curve and could not be consistent with the data. Fluorescence amplitude change, molecular structure and dissociation constant obtained using oxobutyrate (B), oxovalerate (C) and 4-Methyl-2-Oxovalerate (D).