Open Conformation of the Escherichia coli Periplasmic Murein Tripeptide Binding Protein, MppA, at High Resolution.

Forum Bhatt,Constance Jeffery,Vishal Patel

doi:10.3390/biology7020030

Forum Bhatt, Constance Jeffery + Show 1 more

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https://doi.org/10.3390/biology7020030

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Abstract

Periplasmic ligand-binding proteins (PBPs) bind ligands with a high affinity and specificity. They undergo a large conformational change upon ligand binding, and they have a robust protein fold. These physical features have made them ideal candidates for use in protein engineering projects to develop novel biosensors and signaling molecules. The Escherichia coli MppA (murein peptide permease A) PBP binds the murein tripeptide, l-alanyl-γ-d-glutamyl-meso-diaminopimelate, (l-Ala-γ-d-Glu-meso-Dap), which contains both a D-amino acid and a gamma linkage between two of the amino acids. We have solved a high-resolution X-ray crystal structure of E. coli MppA at 1.5 Å resolution in the unliganded, open conformation. Now, structures are available for this member of the PBP protein family in both the liganded/closed form and the unliganded/open form.

Highlights

Periplasmic ligand-binding proteins (PBP) of Gram-negative bacteria and the homologous membrane-bound lipoproteins of Gram-positive bacteria, along with their cognate membrane-embedded permeases, constitute a large class of active transport systems that are responsible for the uptake of sugars, amino acids, anions, peptides, and other nutrients [1]
In order to gain further insight into the conformational changes associated with ligand binding and complete the structural information for this protein, we report here a high-resolution structure of unliganded
As observed with most E. coli PBPs, MppA is processed after amino acid number during its maturation, and the structure begins at amino acid

Summary

Introduction

Periplasmic ligand-binding proteins (PBP) of Gram-negative bacteria and the homologous membrane-bound lipoproteins of Gram-positive bacteria, along with their cognate membrane-embedded permeases, constitute a large class of active transport systems that are responsible for the uptake of sugars, amino acids, anions, peptides, and other nutrients [1]. The three-dimensional X-ray crystal structures of dozens of PBPs have been determined with and without ligands bound Structures include those with a specificity towards various sugars including arabinose [3], galactose [4], ribose [5], and maltose [6], anions including sulfate [7] and phosphate [8], amino acids including histidine [9,10], leucine [11], leucine/isoleucine/valine [12], and lysine/arginine/ornithine [13], oligopeptides [14,15], dipeptides [16,17], and metal ions, including nickel [18]. The open form of the binding proteins exposes a solvent accessible cleft, the closed form encloses the bound

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