Structure, dynamics and domain organization of the repeat protein Cin1 from the apple scab fungus

C.H. Mesarich, M. Schmitz, P. Tremouilhac, D.J. McGillivray, M.D. Templeton, A.J. Dingley

Research output: Contribution to journalArticleAcademicpeer-review

6 Citations (Scopus)


Venturia inaequalis is a hemi-biotrophic fungus that causes scab disease of apple. A recently-identified gene from this fungus, cin1 (cellophane-induced 1), is up-regulated over 1000-fold in planta and considerably on cellophane membranes, and encodes a cysteine-rich secreted protein of 523 residues with eight imperfect tandem repeats of ~ 60 amino acids. The Cin1 sequence has no homology to known proteins and appears to be genus-specific; however, Cin1 repeats and other repeat domains may be structurally similar. An NMR-derived structure of the first two repeat domains of Cin1 (Cin1-D1D2) and a low-resolution model of the full-length protein (Cin1-FL) using SAXS data were determined. The structure of Cin1-D1D2 reveals that each domain comprises a core helix–loop–helix (HLH) motif as part of a three-helix bundle, and is stabilized by two intra-domain disulfide bonds. Cin1-D1D2 adopts a unique protein fold as DALI and PDBeFOLD analysis identified no structural homology. A 15N backbone NMR dynamic analysis of Cin1-D1D2 showed that a short stretch of the inter-domain linker has large amplitude motions that give rise to reciprocal domain–domain mobility. This observation was supported by SAXS data modeling, where the scattering length density envelope remains thick at the domain–domain boundary, indicative of inter-domain dynamics. Cin1-FL SAXS data models a loosely-packed arrangement of domains, rather than the canonical parallel packing of adjacent HLH repeats observed in a-solenoid repeat proteins. Together, these data suggest that the repeat domains of Cin1 display a “beads-on-a-string” organization with inherent inter-domain flexibility that is likely to facilitate interactions with target ligands.
Original languageEnglish
Pages (from-to)1118-1128
JournalBiochimica et Biophysica Acta. Proteins & Proteomics
Issue number10
Publication statusPublished - 2012


  • model-free approach
  • magnetic-resonance relaxation
  • nmr structure determination
  • ray solution scattering
  • torsion angle dynamics
  • cell-wall protein
  • venturia-inaequalis
  • zinc-fingers
  • helicobacter-pylori
  • backbone dynamics


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