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Sequence dependence of kinetics and morphology of collagen model peptide self-assembly into higher order structures

¹ Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA
² Biochemistry Department, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA

(RECEIVED January 8, 2008; FINAL REVISION March 24, 2008; ACCEPTED March 26, 2008)

The process of self-assembly of the triple-helical peptide (Pro-Hyp-Gly)₁₀ into higher order structure resembles the nucleation-growth mechanism of collagen fibril formation in many features, but the irregular morphology of the self-assembled peptide contrasts with the ordered fibers and networks formed by collagen in vivo. The amino acid sequence in the central region of the (Pro-Hyp-Gly)₁₀ peptide was varied and found to affect the kinetics of self-assembly and nature of the higher order structure formed. Single amino acid changes in the central triplet produced irregular higher order structures similar to (Pro-Hyp-Gly)_10,, but the rate of self-association was markedly delayed by a single change in one Pro to Ala or Leu. The introduction of a Hyp-rich hydrophobic sequence from type IV collagen resulted in a more regular suprastructure of extended fibers that sometimes showed supercoiling and branching features similar to those seen for type IV collagen in the basement membrane network. Several peptides, where central Pro-Hyp sequences were replaced by charged residues or a nine-residue hydrophobic region from type III collagen, lost the ability to self-associate under standard conditions. The inability to self-assemble likely results from loss of imino acids, and lack of an appropriate distribution of hydrophobic/electrostatic residues. The effect of replacement of a single Gly residue was also examined, as a model for collagen diseases such as osteogenesis imperfecta and Alport syndrome. Unexpectedly, the Gly to Ala replacement interfered with self-assembly of (Pro-Hyp-Gly)₁₀, while the peptide with a Gly to Ser substitution self-associated to form a fibrillar structure.

Keywords: triple helix; collagen; self-assembly; fibrils; peptides

Reprint requests to: Barbara Brodsky, Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, 675 Hoes Lane, Piscataway, NJ 08854, USA; e-mail: brodsky{at}umdnj.edu; fax: (732) 235-4783.

Abbreviations: CD, circular dichroism; DSC, differential scanning calorimetry; OI, osteogenesis imperfecta; PBS, phosphate buffer saline; (POG)₁₀, (Pro-Hyp-Gly)₁₀, and O is used to represent hydroxyproline in the one-letter amino acid code.

Article published online ahead of print. Article and publication date are at http://www.proteinscience.org/cgi/doi/10.1110/ps.083441308.

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