Crystal structures of various maltooligosaccharides bound to maltoporin reveal a specific sugar translocation pathway.

Structural Basis for Sugar Translocation Through Maltoporin Channels at 3.1 A Resolution

VDFHGYARSGIGWTGSGGEQQCFQTTGAQSKYRLGNECETYAELKLGQEVWKEGDKSFYFDTNVAYSVAQQNDWEATDPA
FREANVQGKNLIEWLPGSTIWAGKRFYQRHDVHMIDFYYWDISGPGAGLENIDVGFGKLSLAATRSSEAGGSSSFASNNI
YDYTNETANDVFDVRLAQMEINPGGTLELGVDYGRANLRDNYRLVDGASKDGWLFTAEHTQSVLKGFNKFVVQYATDSMT
SQGKGLSQGSGVAFDNEKFAYNINNNGHMLRILDHGAISMGDNWDMMYVGMYQDINWDNDNGTKWWTVGIRPMYKWTPIM
STVMEIGYDNVESQRTGDKNNQYKITLAQQWQAGDSIWSRPAIRVFATYAKWDEKWGYDYTGNADNNANFGKAVPADFNG
GSFGRGDSDEWTFGAQMEIWW

MALTOSE CONSISTS OF TWO ALPHA-1-4 LINKED GLUCOSYL RESIDUES. THE GLUCOSYL RESIDUES OF THE TWO MALTOSE MOLECULES ARE RESIDUES 431 - 432 AND 441 - 442 RESPECTIVELY. THE TWO MOLECULES OVERLAP AND REPRESENT ALTERNATIVE BINDING MODES. AN OCCUPANCY OF 0.5 HAS BEEN ASSIGNED TO THE TWO MALTOSE MOLECULES. THE TWO MALTOSE POSITIONS ARE SLIGHTLY OVERLAPPING. INTERACTION BETWEEN THE TWO MALTOSE MOLECULES WAS EXCLUDED DURING REFINEMENT.

THE ASYMMETRIC UNIT CONTAINS THREE MONOMERS A, B, AND C. CHAINS B AND C OF THE ENTRY HAVE BEEN GENERATED BY THE PDB TO PROVIDE THE OTHER TWO SUBUNITS OF THE MOLECULAR THREE-FOLD TRIMER.

MEMBRANE PROTEIN, SUGAR TRANSPORT, SPECIFIC PORIN, BETA BARREL

MMITLRKLPLAVAVAAGVMSAQAMAVDFHGYARSGIGWTGSGGEQQCFQTTGAQSKYRLGNECETYAELKLGQEVWKEGD
KSFYFDTNVAYSVAQQNDWEATDPAFREANVQGKNLIEWLPGSTIWAGKRFYQRHDVHMIDFYYWDISGPGAGLENIDVG
FGKLSLAATRSSEAGGSSSFASNNIYDYTNETANDVFDVRLAQMEINPGGTLELGVDYGRANLRDNYRLVDGASKDGWLF
TAEHTQSVLKGFNKFVVQYATDSMTSQGKGLSQGSGVAFDNEKFAYNINNNGHMLRILDHGAISMGDNWDMMYVGMYQDI
NWDNDNGTKWWTVGIRPMYKWTPIMSTVMEIGYDNVESQRTGDKNNQYKITLAQQWQAGDSIWSRPAIRVFATYAKWDEK
WGYDYTGNADNNANFGKAVPADFNGGSFGRGDSDEWTFGAQMEIWW