Article Abstract:
The GroES heptamer forms a dome about 75 angstroms in diameter and 30 angstroms in height, having an eight angstroms cavity in the middle of its roof. The mobile loop segment has six subunits, which form anti-parallel beta-barrels with beta-hairpins extending out from the top. The beta-barrels are arranged in a ring with their axes parallel to each other. Interactions between adjacent beta-barrels hold the ring. The residues near the mobile loop are placed at the bottom outer rim of the dome, indicating that the region is an intermediary in binding GroEL.
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Article Abstract:
The crystal structure of the leucine-rich repeat at 2.5 Angstrom resolution reveals that the repeat consists of a ribonuclease inhibitor and ribonculease A on both sides of the leucine molecule. The repeat is a motif widely used in molecular recognition processes such as signal transduction, cell development, cell adhesion, RNA processing and DNA repair. The leucine-rich repeats function as effective protein binding motifs since they utilize the solvent-exposed parallel beta-sheet and non-globular structure of the ribonuclease inhibitor.
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Article Abstract:
Protein cell function can be controlled in several ways. Structurally characterized examples where control is mediated by active site-directed, intasteric autoregulatory sequences (IARS) are described. The examples of intrasteric regulation confirm predictions that pseudosubstrates operate at the active site and that contacts made by the inhibitory segments do not simply mimic the substrates.
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