Glycosylated polyproline II rods with kinks as a structural motif in plant hydroxyproline-rich glycoproteins

Biochemistry. 2001 Mar 6;40(9):2978-87. doi: 10.1021/bi0023605.


Hydroxyproline-rich glycoproteins (HRGPs) are the major proteinaceous components of higher plant walls and the predominant components of the cell wall of the green alga Chlamydomonas reinhardtii. The GP1 protein, an HRGP of the C. reinhardtii wall, is shown to adopt a polyproline II helical configuration and to carry a complex array of arabinogalactoside residues, many branched, which are necessary to stabilize the helical conformation. The deduced GP1 amino acid sequence displays two Ser-Pro-rich domains, one with a repeating (SP)(x)() motif and the other with a repeating (PPSPX)(x)() motif. A second cloned gene a2 also carries the PPSPX repeat, defining a novel gene family in this lineage. The SP-repeat domains of GP1 form a 100-nm shaft with a flexible kink 28 nm from the head. The gp1 gene encodes a PPPPPRPPFPANTPM sequence at the calculated kink position, generating the proposal that this insert interrupts the PPII helix, with the resultant kink exposing amino acids necessary for GP1 to bind to partner molecules. It is proposed that similar kinks in the higher plant HRGPs called extensins may play a comparable role in wall assembly.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Carbohydrate Conformation
  • Carbohydrates / analysis
  • Chlamydomonas reinhardtii / chemistry
  • Chlamydomonas reinhardtii / genetics
  • Cloning, Molecular
  • Genes, Plant
  • Glycoproteins / chemistry
  • Glycoproteins / genetics
  • Glycoproteins / metabolism*
  • Glycosylation
  • Hydroxyproline / chemistry
  • Hydroxyproline / metabolism*
  • Molecular Sequence Data
  • Peptides / chemistry
  • Peptides / metabolism*
  • Plant Proteins / chemistry
  • Plant Proteins / genetics
  • Plant Proteins / metabolism*
  • Protein Structure, Secondary
  • Protein Structure, Tertiary


  • Carbohydrates
  • Glycoproteins
  • Peptides
  • Plant Proteins
  • extensin protein, plant
  • polyproline
  • Hydroxyproline