5MKB image
Entry Detail
PDB ID:
5MKB
Title:
Maltodextrin binding protein MalE1 from L. casei BL23 without ligand
Biological Source:
Source Organism:
PDB Version:
Deposition Date:
2016-12-03
Release Date:
2017-07-05
Method Details:
Experimental Method:
Resolution:
1.70 Å
R-Value Free:
0.21
R-Value Work:
0.17
R-Value Observed:
0.18
Space Group:
P 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:MalE1
Chain IDs:A, B, C, D, E, F, G, H
Chain Length:379
Number of Molecules:8
Biological Source:Lactobacillus casei
Primary Citation
Inducer exclusion in Firmicutes: insights into the regulation of a carbohydrate ATP binding cassette transporter from Lactobacillus casei BL23 by the signal transducing protein P-Ser46-HPr.
Mol. Microbiol. 105 25 45 (2017)
PMID: 28370477 DOI: 10.1111/mmi.13680

Abstact

Catabolite repression is a mechanism that enables bacteria to control carbon utilization. As part of this global regulatory network, components of the phosphoenolpyruvate:carbohydrate phosphotransferase system inhibit the uptake of less favorable sugars when a preferred carbon source such as glucose is available. This process is termed inducer exclusion. In bacteria belonging to the phylum Firmicutes, HPr, phosphorylated at serine 46 (P-Ser46-HPr) is the key player but its mode of action is elusive. To address this question at the level of purified protein components, we have chosen a homolog of the Escherichia coli maltose/maltodextrin ATP-binding cassette transporter from Lactobacillus casei (MalE1-MalF1G1K12) as a model system. We show that the solute binding protein, MalE1, binds linear and cyclic maltodextrins but not maltose. Crystal structures of MalE1 complexed with these sugars provide a clue why maltose is not a substrate. P-Ser46-HPr inhibited MalE1/maltotetraose-stimulated ATPase activity of the transporter incorporated in proteoliposomes. Furthermore, cross-linking experiments revealed that P-Ser46-HPr contacts the nucleotide-binding subunit, MalK1, in proximity to the Walker A motif. However, P-Ser46-HPr did not block binding of ATP to MalK1. Together, our findings provide first biochemical evidence that P-Ser-HPr arrests the transport cycle by preventing ATP hydrolysis at the MalK1 subunits of the transporter.

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