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| - | [[Image:1htx.gif|left|200px]] | + | {{Seed}} |
| | + | [[Image:1htx.png|left|200px]] |
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| | {{STRUCTURE_1htx| PDB=1htx | SCENE= }} | | {{STRUCTURE_1htx| PDB=1htx | SCENE= }} |
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| - | '''SOLUTION STRUCTURE OF THE MAIN ALPHA-AMYLASE INHIBITOR FROM AMARANTH SEEDS'''
| + | ===SOLUTION STRUCTURE OF THE MAIN ALPHA-AMYLASE INHIBITOR FROM AMARANTH SEEDS=== |
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| - | ==Overview==
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| - | The most abundant alpha-amylase inhibitor (AAI) present in the seeds of Amaranthus hypochondriacus, a variety of the Mexican crop plant amaranth, is the smallest polypeptide (32 residues) known to inhibit alpha-amylase activity of insect larvae while leaving that of mammals unaffected. In solution, 1H NMR reveals that AAI isolated from amaranth seeds adopts a major trans (70%) and minor cis (30%) conformation, resulting from slow cis-trans isomerization of the Val15-Pro16 peptide bond. Both solution structures have been determined using 2D 1H-NMR spectroscopy and XPLOR followed by restrained energy refinement in the consistent-valence force field. For the major isomer, a total of 563 distance restraints, including 55 medium-range and 173 long-range ones, were available from the NOESY spectra. This rather large number of constraints from a protein of such a small size results from a compact fold, imposed through three disulfide bridges arranged in a cysteine-knot motif. The structure of the minor cis isomer has also been determined using a smaller constraint set. It reveals a different backbone conformation in the Pro10-Pro20 segment, while preserving the overall global fold. The energy-refined ensemble of the major isomer, consisting of 20 low-energy conformers with an average backbone rmsd of 0.29 +/- 0.19 A and no violations larger than 0.4 A, represents a considerable improvement in precision over a previously reported and independently performed calculation on AAI obtained through solid-phase synthesis, which was determined with only half the number of medium-range and long-range restraints reported here, and featured the trans isomer only. The resulting differences in ensemble precision have been quantified locally and globally, indicating that, for regions of the backbone and a good fraction of the side chains, the conformation is better defined in the new solution structure. Structural comparison of the solution structure with the X-ray structure of the inhibitor when bound to its alpha-amylase target in Tenebrio molitor shows that the backbone conformation is only slightly adjusted on complexation, while that of the side chains involved in protein-protein contacts is similar to those present in solution. Therefore, the overall conformation of AAI appears to be predisposed to binding to its target alpha-amylase, confirming the view that it acts as a lid on top of the alpha-amylase active site. | + | The line below this paragraph, {{ABSTRACT_PUBMED_11298757}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 11298757 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_11298757}} |
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| | ==About this Structure== | | ==About this Structure== |
| - | 1HTX is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Amaranthus_hypochondriacus Amaranthus hypochondriacus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1HTX OCA]. | + | 1HTX is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Amaranthus_hypochondriacus Amaranthus hypochondriacus]. Full experimental information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1HTX OCA]. |
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| | ==Reference== | | ==Reference== |
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| | [[Category: Wodak, S J.]] | | [[Category: Wodak, S J.]] |
| | [[Category: Cysteine knot]] | | [[Category: Cysteine knot]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 19:13:40 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 08:40:17 2008'' |
Revision as of 05:40, 1 July 2008
Template:STRUCTURE 1htx
SOLUTION STRUCTURE OF THE MAIN ALPHA-AMYLASE INHIBITOR FROM AMARANTH SEEDS
Template:ABSTRACT PUBMED 11298757
About this Structure
1HTX is a Single protein structure of sequence from Amaranthus hypochondriacus. Full experimental information is available from OCA.
Reference
Solution structure of the main alpha-amylase inhibitor from amaranth seeds., Martins JC, Enassar M, Willem R, Wieruzeski JM, Lippens G, Wodak SJ, Eur J Biochem. 2001 Apr;268(8):2379-89. PMID:11298757
Page seeded by OCA on Tue Jul 1 08:40:17 2008
