SSF50692

ADC-like

SUPERFAMILY entry
Member databaseSUPERFAMILY
SUPERFAMILY typehomologous superfamily

Description
Imported from IPR009010

β-barrels are commonly observed in protein structures. They are classified in terms of two integral parameters: the number of strands in the sheet, n, and the shear number, S, a measure of the stagger of the strands in the β-sheet. These two parameters have been shown to determine the major geometrical features of β-barrels. Six-stranded β-barrels with a pseudo-twofold axis are found in several proteins. One involving parallel strands forming two psi structures is known as the double-psi barrel. The first psi structure consists of the loop connecting strands β1 and β2 (a 'psi loop') and the strand β5, whereas the second psi structure consists of the loop connecting strands β4 and β5 and the strand β2. All the psi structures in double-psi barrels have a unique handedness, in that β1 (β4), β2 (β5) and the loop following β5 (β2) form a right-handed helix. The unique handedness may be related to the fact that the twisting angle between the parallel pair of strands is always larger than that between the antiparallel pair
[1]
.

In many cases, including aspartate decarboxylase and aspartic proteinases, strands 1 and 4 are each bent and consist of two sections. The two sections normally make a right angle; sometimes their hydrogen-bond patterns are disrupted at the corner by a bulge or even by a large insertion. In these cases, the barrel can also be viewed as a pair of orthogonally packed sheets, each with four strands.

References
Imported from IPR009010

1.A six-stranded double-psi beta barrel is shared by several protein superfamilies. Castillo RM, Mizuguchi K, Dhanaraj V, Albert A, Blundell TL, Murzin AG. Structure 7, 227-36, (1999). View articlePMID: 10368289

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