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Figure 1 | BMC Structural Biology

Figure 1

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

Figure 1

Binding of 2-keto acids to TakP. A: The amplitude of the integrated fluorescence band (normalized to its extent in the absence of ligand) was plotted as a function of the concentration of added pyruvate. The concentration of binding sites (monomeric unit) was 50 nM. The solid line is a fit with the equation given in the text, yielding K d ≈ 270 nM. The dashed line is a numerical simulation of a (slightly) cooperative model, assuming that the first binding event occurs with K d (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. B-D: Fluorescence amplitude change, molecular structure and dissociation constant obtained using oxobutyrate (B), oxovalerate (C) and 4-Methyl-2-Oxovalerate (D).

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BMC Structural Biology

ISSN: 1472-6807

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