1b9u: Difference between revisions

[[Image:1b9u.jpg|left|200px]]<br /><applet load="1b9u" size="350" color="white" frame="true" align="right" spinBox="true"  

The structure of the N-terminal transmembrane domain (residues 1-34) of subunit b of the Escherichia coli F0F1-ATP synthase has been solved by two-dimensional 1H NMR in a membrane mimetic solvent mixture of chloroform/methanol/H2O (4:4:1). Residues 4-22 form an alpha-helix, which is likely to span the hydrophobic domain of the lipid bilayer to anchor the largely hydrophilic subunit b in the membrane. The helical structure is interrupted by a rigid bend in the region of residues 23-26 with alpha-helical structure resuming at Pro-27 at an angle offset by 20 degrees from the transmembrane helix. In native subunit b, the hinge region and C-terminal alpha-helical segment would connect the transmembrane helix to the cytoplasmic domain. The transmembrane domains of the two subunit b in F0 were shown to be close to each other by cross-linking experiments in which single Cys were substituted for residues 2-21 of the native subunit and b-b dimer formation tested after oxidation with Cu(II)(phenanthroline)2. Cys residues that formed disulfide cross-links were found with a periodicity indicative of one face of an alpha-helix, over the span of residues 2-18, where Cys at positions 2, 6, and 10 formed dimers in highest yield. A model for the dimer is presented based upon the NMR structure and distance constraints from the cross-linking data. The transmembrane alpha-helices are positioned at a 23 degrees angle to each other with the side chains of Thr-6, Gln-10, Phe-14, and Phe-17 at the interface between subunits. The change in direction of helical packing at the hinge region may be important in the functional interaction of the cytoplasmic domains.

1B9U is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/ ]. Active as [http://en.wikipedia.org/wiki/H(+)-transporting_two-sector_ATPase H(+)-transporting two-sector ATPase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.6.3.14 3.6.3.14] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1B9U OCA].  

[[Category: Fillingame, R H.]]

[[Category: Jones, P C.]]

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