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Crystal structures of CusC review conformational changes accompanying folding and transmembrane channel formation.

ABSTRACT: Gram-negative bacteria, such as Escherichia coli, frequently utilize tripartite efflux complexes in the RND (resistance-nodulation-cell division) family to expel diverse toxic compounds from the cell. These complexes span both the inner and outer membranes of the bacterium via an ?-helical, inner membrane transporter; a periplasmic membrane fusion protein; and a ?-barrel, outer membrane channel. One such efflux system, CusCBA, is responsible for extruding biocidal Cu(I) and Ag(I) ions. To remove these toxic ions, the CusC outer membrane channel must form a ?-barrel structural domain, which creates a pore and spans the entire outer membrane. We here report the crystal structures of wild-type CusC, as well as two CusC mutants, suggesting that the first N-terminal cysteine residue plays an important role in protein-membrane interactions and is critical for the insertion of this channel protein into the outer membrane. These structures provide insight into the mechanisms on CusC folding and transmembrane channel formation. It is found that the interactions between CusC and membrane may be crucial for controlling the opening and closing of this ?-barrel, outer membrane channel.

SUBMITTER: Lei HT

PROVIDER: S-EPMC4800009 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature

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Crystal structures of CusC review conformational changes accompanying folding and transmembrane channel formation.

Lei Hsiang-Ting HT Bolla Jani Reddy JR Bishop Nicholas R NR Su Chih-Chia CC Yu Edward W EW

Journal of molecular biology 20131004 2

Gram-negative bacteria, such as Escherichia coli, frequently utilize tripartite efflux complexes in the RND (resistance-nodulation-cell division) family to expel diverse toxic compounds from the cell. These complexes span both the inner and outer membranes of the bacterium via an α-helical, inner membrane transporter; a periplasmic membrane fusion protein; and a β-barrel, outer membrane channel. One such efflux system, CusCBA, is responsible for extruding biocidal Cu(I) and Ag(I) ions. To remove ...[more]

PMID: 24099674

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Project description:In order for protein kinases to exchange nucleotide they must open and close their catalytic cleft. These motions are associated with rotations of the N-lobe, predominantly around the 'hinge region'. We conducted an analysis of 28 crystal structures of the serine-threonine kinase, p21-activated kinase 4 (PAK4), including three newly determined structures in complex with staurosporine, FRAX486, and fasudil (HA-1077). We find an unusual motion between the N-lobe and C-lobe of PAK4 that manifests as a partial unwinding of helix αC. Principal component analysis of the crystal structures rationalizes these movements into three major states, and analysis of the kinase hydrophobic spines indicates concerted movements that create an accessible back pocket cavity. The conformational changes that we observe for PAK4 differ from previous descriptions of kinase motions, and although we observe these differences in crystal structures there is the possibility that the movements observed may suggest a diversity of kinase conformational changes associated with regulation.Author summaryProtein kinases are key signaling proteins, and are important drug targets, therefore understanding their regulation is important for both basic research and clinical points of view. In this study, we observe unusual conformational 'hinging' for protein kinases. Hinging, the opening and closing of the kinase sub-domains to allow nucleotide binding and release, is critical for proper kinase regulation and for targeted drug discovery. We determine new crystal structures of PAK4, an important Rho-effector kinase, and conduct analyses of these and previously determined structures. We find that PAK4 crystal structures can be classified into specific conformational groups, and that these groups are associated with previously unobserved hinging motions and an unusual conformation for the kinase hydrophobic core. Our findings therefore indicate that there may be a diversity of kinase hinging motions, and that these may indicate different mechanisms of regulation.

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Crystal structures of CusC review conformational changes accompanying folding and transmembrane channel formation.

Publications

Crystal structures of CusC review conformational changes accompanying folding and transmembrane channel formation.

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