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Title
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Crystal structure of porcine ribonuclease inhibitor, a protein with leucine-rich repeats.
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Authors
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B.Kobe,
J.Deisenhofer.
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Ref.
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Nature, 1993,
366,
751-756.
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PubMed id
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Abstract
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Ribonuclease inhibitor is a cytoplasmic protein that tightly binds and inhibits
ribonucleases of the pancreatic ribonuclease superfamily. The primary sequence
of this inhibitor contains leucine-rich repeats (LRRs); these motifs are present
in many proteins that participate in protein-protein interactions and have
different functions and cellular locations. In vivo, ribonuclease inhibitor may
have a role in the regulation of RNA turnover in mammalian cells and in
angiogenesis. To define the structural features of LRR proteins and to
understand better the nature of the tight interaction of ribonuclease inhibitor
with ribonucleases, we have determined the crystal structure of the porcine
inhibitor. To our knowledge, this is the first three-dimensional structure of a
protein containing LRRs and represents a new class of alpha/beta protein fold.
Individual repeats constitute beta-alpha structural units that probably also
occur in other proteins containing LRRs. The non-globular shape of the structure
and the exposed face of the parallel beta-sheet may explain why LRRs are used to
achieve strong protein-protein interactions. A possible ribonuclease-binding
region incorporates the surface formed by the parallel beta-sheet and the beta
alpha loops.
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