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Psi loops

Psi-loops consist of two antiparallel strands linked by a '+2' connection (Richardson, 1981) i.e. with one strand in between, hydrogen bonded to both of them (Tang et al., 1978) In contrast to the beta-alpha-beta units these occur very rarely in proteins (Hutchinson & Thornton, 1990). Just the start and end residues of each of the two strands involved are included at the moment.

References

Hutchinson EG and Thornton JM (1990). HERA - A program to draw schematic diagrams of protein secondary structure. Proteins Struct. Funct. Genet., 8, 203-212.
Richardson JS (1981) The anatomy and taxonomy of protein structure. Adv. Protein Chem. 34, 167-339.
Tang J, James MNG, Hsu IN, Jenkins JA and Blundell TL (1978). Structural evidence for gene duplication in the evolution of the acid proteases. Nature, 271, 618-621.

 

Gail Hutchinson 22nd May, 1996 spacer
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