A Comparison of the Self-association Behavior of the Plant Cyclotides Kalata B1 and Kalata B2 via Analytical Ultracentrifugation
A Comparison of the Self-association Behavior of the Plant Cyclotides Kalata B1 and Kalata B2 via Analytical Ultracentrifugation
Engineering Village 2
? 2006 Elsevier Inc
Accession number: 04037820475
Title: A Comparison of the Self-association Behavior of the Plant Cyclotides Kalata B1 and Kalata B2 via Analytical Ultracentrifugation
Authors: Nourse, Amanda; Trabi, Manuela; Daly, Norelle L.; Craik, David J.
Author affiliation: Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia
Serial title: Journal of Biological Chemistry
Abbreviated serial title: J. Biol. Chem.
Volume: v 279
Issue: n 1
Issue date: Jan 2 2004
Publication year: 2004
Pages: p 562-570
Language: English
ISSN: 0021-9258
CODEN: JBCHA3
Document type: Journal article (JA)
Publisher: American Society for Biochemistry and Molecular Biology Inc.
Abstract: The recently discovered cyclotides kalata B1 and kalata B2 are miniproteins containing a head-to-tail cyclized backbone and a cystine knot motif, in which disulfide bonds and the connecting backbone segments form a ring that is penetrated by the third disulfide bond. This arrangement renders the cyclotides extremely stable against thermal and enzymatic decay, making them a possible template onto which functionalities can be grafted. We have compared the hydrodynamic properties of two prototypic cyclotides, kalata B1 and kalata B2, using analytical ultracentrifugation techniques. Direct evidence for oligomerization of kalata B2 was shown by sedimentation velocity experiments in which a method for determining size distribution of polydisperse molecules in solution was employed. The shape of the oligomers appears to be spherical. Both sedimentation velocity and equilibrium experiments indicate that in phosphate buffer kalata B1 exists mainly as a monomer, even at millimolar concentrations. In contrast, at 1.6 mM, kalata B2 exists as an equilibrium mixture of monomer (30%), tetramer (42%), octamer (25%), and possibly a small proportion of higher oligomers. The results from the sedimentation equilibrium experiments show that this self-association is concentration dependent and reversible. We link our findings to the three-dimensional structures of both cyclotides, and propose two putative interaction interfaces on opposite sides of the kalata B2 molecule, one involving a hydrophobic interaction with the Phe6, and the second involving a charge-charge interaction with the Asp25 residue. An understanding of the factors affecting solution aggregation is of vital importance for future pharmaceutical application of these molecules.
Number of references: 31
Ei main heading: Biochemistry
Ei controlled terms: Plants (botany) - Proteins - Oligomers - Drug products - Monomers - Hydrophobicity - Centrifugation - Agglomeration - Hydrodynamics
Uncontrolled terms: Self-association behavior
Ei classification codes: 801.2 Biochemistry - 461.9 Biology - 804.1 Organic Compounds - 815.1.1 Organic Polymers - 461.6 Medicine - 931.2 Physical Properties of Gases, Liquids & Solids - 802.3 Chemical Operations
Treatment: Theoretical (THR); Experimental (EXP)
DOI: 10.1074/jbc.M306826200
Database: Compendex
Compilation and indexing terms, ? 2006 Elsevier Inc. All rights reserved
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