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PDBsum entry 5mmt
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Transport protein
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PDB id
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5mmt
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References listed in PDB file
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Key reference
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Title
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Structure determination of a major facilitator peptide transporter: inward facing peptst from streptococcus thermophilus crystallized in space group p3121.
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Authors
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E.M.Quistgaard,
M.Martinez molledo,
C.Löw.
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Ref.
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PLoS One, 2017,
12,
e0173126.
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PubMed id
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Abstract
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Major facilitator superfamily (MFS) peptide transporters (typically referred to
as PepT, POT or PTR transporters) mediate the uptake of di- and tripeptides, and
so play an important dietary role in many organisms. In recent years, a better
understanding of the molecular basis for this process has emerged, which is in
large part due to a steep increase in structural information. Yet, the
conformational transitions underlying the transport mechanism are still not
fully understood, and additional data is therefore needed. Here we report in
detail the detergent screening, crystallization, experimental MIRAS phasing, and
refinement of the peptide transporter PepTSt from Streptococcus thermophilus.
The space group is P3121, and the protein is crystallized in a monomeric inward
facing form. The binding site is likely to be somewhat occluded, as the lobe
encompassing transmembrane helices 10 and 11 is markedly bent towards the
central pore of the protein, but the extent of this potential occlusion could
not be determined due to disorder at the apex of the lobe. Based on structural
comparisons with the seven previously determined P212121 and C2221 structures of
inward facing PepTSt, the structural flexibility as well as the conformational
changes mediating transition between the inward open and inward facing occluded
states are discussed. In conclusion, this report improves our understanding of
the structure and conformational cycle of PepTSt, and can furthermore serve as a
case study, which may aid in supporting future structure determinations of
additional MFS transporters or other integral membrane proteins.
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