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1gaj
From Proteopedia
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| , resolution 2.50Å | |||||||
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| Ligands: | , , and | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
CRYSTAL STRUCTURE OF A NUCLEOTIDE-FREE ATP-BINDING CASSETTE FROM AN ABC TRANSPORTER
Overview
BACKGROUND: ATP binding cassette (ABC) transporters are ubiquitously distributed transmembrane solute pumps that play a causative role in numerous diseases. Previous structures have defined the fold of the ABC and established the flexibility of its alpha-helical subdomain. But the nature of the mechanical changes that occur at each step of the chemical ATPase cycle have not been defined. RESULTS: Crystal structures were determined of the MJ1267 ABC from Methanococcus jannaschii in Mg-ADP-bound and nucleotide-free forms. Comparison of these structures reveals an induced-fit effect at the active site likely to be a consequence of nucleotide binding. In the Mg-ADP-bound structure, the loop following the Walker B moves toward the Walker A (P-loop) coupled to backbone conformational changes in the intervening "H-loop", which contains an invariant histidine. These changes affect the region believed to mediate intercassette interaction in the ABC transporter complex. Comparison of the Mg-ADP-bound structure of MJ1267 to the ATP-bound structure of HisP suggests that an outward rotation of the alpha-helical subdomain is coupled to the loss of a molecular contact between the gamma-phosphate of ATP and an invariant glutamine in a segment connecting this subdomain to the core of the cassette. CONCLUSIONS: The induced-fit effect and rotation of the alpha-helical subdomain may play a role in controlling the nucleotide-dependent change in cassette-cassette interaction affinity believed to represent the power-stroke of ABC transporters. Outward rotation of the alpha-helical subdomain also likely facilitates Mg-ADP release after hydrolysis. The MJ1267 structures therefore define features of the nucleotide-dependent conformational changes that drive transmembrane transport in ABC transporters.
About this Structure
1GAJ is a Single protein structure of sequence from Methanocaldococcus jannaschii. Full crystallographic information is available from OCA.
Reference
Crystal structures of the MJ1267 ATP binding cassette reveal an induced-fit effect at the ATPase active site of an ABC transporter., Karpowich N, Martsinkevich O, Millen L, Yuan YR, Dai PL, MacVey K, Thomas PJ, Hunt JF, Structure. 2001 Jul 3;9(7):571-86. PMID:11470432
Page seeded by OCA on Thu Mar 20 11:20:32 2008
