Abstract
We determined at 2.3 A resolution the crystal structure of prophytepsin, a zymogen of a barley vacuolar aspartic proteinase. In addition to the classical pepsin-like bilobal main body of phytepsin, we also traced most of the propeptide, as well as an independent plant-specific domain, never before described in structural terms. The structure revealed that, in addition to the propeptide, 13 N-terminal residues of the mature phytepsin are essential for inactivation of the enzyme. Comparison of the plant-specific domain with NK-lysin indicates that these two saposin-like structures are closely related, suggesting that all saposins and saposin-like domains share a common topology. Structural analysis of prophytepsin led to the identification of a putative membrane receptor-binding site involved in Golgi-mediated transport to vacuoles.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Aspartic Acid Endopeptidases / chemistry*
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Aspartic Acid Endopeptidases / metabolism
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Biological Transport
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Cathepsins / chemistry*
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Cathepsins / metabolism
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Crystallography, X-Ray
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Disulfides / chemistry
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Electrons
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Enzyme Activation
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Enzyme Precursors / chemistry*
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Enzyme Precursors / metabolism
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Glycoproteins / chemistry
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Golgi Apparatus / metabolism
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Hordeum / cytology
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Hordeum / enzymology*
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Hordeum / metabolism
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Hydrogen Bonding
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Models, Molecular
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Molecular Sequence Data
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Protein Conformation
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Protein Structure, Secondary
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Proteolipids / chemistry
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Pulmonary Surfactants / chemistry
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Receptors, Cell Surface / metabolism
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Saposins
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Sequence Homology, Amino Acid
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Vacuoles / enzymology*
Substances
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Disulfides
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Enzyme Precursors
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Glycoproteins
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NK-lysin
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Proteolipids
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Pulmonary Surfactants
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Receptors, Cell Surface
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Saposins
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Cathepsins
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Aspartic Acid Endopeptidases
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phytepsin