Evidence for a repeating cross-beta sheet structure in the adenovirus fibre
Green, N.M.; Wrigley, N.G.; Russell, W.C.; Martin, S.R.; Mclachlan, A.D.
EMBO Journal 2(8): 1357-1365
1983
ISSN/ISBN: 0261-4189 PMID: 10872331 Document Number: 218344
The amino acid sequence of the adenovirus fiber protein reveals an approximately repeating motif of 15 residues. A diagonal comparison with established that these repeats extended from residue 43 to residue 400 of the 581 residue sequence. Assignment of secondary structure combined with model building showed that each 15-residue segment contained 2 short .beta.-strands and 2 .beta.-bends, one of which incorporated an extra residue in a .beta.-bulge of the Gx type. The 44 strands together gave a long (210 .ANG.), narrow, amphiphatic .beta.-sheet, which could be stablized by dimer formation to give the shaft of the fiber. The knob could arise from a dimer of the C-terminal 180 residue segment, predicted to be an 8-10 stranded .beta.-sandwich. This model is consistent with the electron micrographs of the fiber and it was supported by measurements of circular dichroism and of electron diffraction from microcrystals. The latter gave a pair of wide angle arcs, corresponding to a repeat of 4.7 .ANG., oriented appropriately for a cross-.beta. structure. The relation of this structure to globular structures is discussed and a folding pathway is proposed. In its general features the structure resembles that proposed for the tail fiber of bacteriophage T4.