beta sheet

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beta sheet

n.
A secondary structure that occurs in many proteins and consists of two or more parallel adjacent polypeptide chains arranged in such a way that hydrogen bonds can form between the chains. Also called beta pleated sheet, pleated sheet.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

beta sheet

A protein configuration resulting from the alignment of multiple adjacent beta strands and formation of hydrogen bonds between them. The beta sheet is a major secondary protein structure motif elucidated by Pauling and Corey, which consists of polypeptide chains in sheets laid side-by-side and are almost completely extended, with an axial distance of 35 nm vs an axial distance of 15 nm in the helix. The PS is stabilised by hydrogen bonds between NH and CO groups of different polypeptide strands; adjacent molecules may run in the same direction (parallel) or in the opposite (antiparallel) direction—e.g., silk fibroin. The PS is a tertiary structure elucidated by X-ray crystallography and seen by EM; it can be produced experimentally by treating Bence-Jones proteins with enzymes, and is a structure typical of amyloidosis. The PS may be seen by the Congo red stain with polarising light to reveal the characteristic apple-green birefringence.
 
EM
Extracellular 700–1000 nm in diameter, fine complex non-branching fibrils.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

beta sheet

A protein structure in which parallel layers of linked peptides are folded across each other. This structure is characteristic of amyloid proteins.
See also: sheet
Medical Dictionary, © 2009 Farlex and Partners
References in periodicals archive ?
In general, [Mn.sup.2+] binding aspartic acid residue is usually surrounded by hydrophobic amino acids (Val, Ile, and Leu) which form beta strand in the N-terminal direction and coil formers (His, Asp, Asn, Pro, and Gly) in the C-terminal direction.
More than 60% of amino acid residues in -4 and -3 positions form beta strand (see Figure 1(a)).
Beta strand can rarely be found near the Asp residue which is not involved in [Mn.sup.2+] binding.
There is a clear preference for asymmetric secondary structure distribution around aspartic acid residues providing oxygen atoms from their side chains for [Mn.sup.2+] coordination: beta strand is situated in the N-terminal direction, while random coil is situated in the C-terminal direction.
Beta strand is the preferable type of secondary structure for positions from -5 to 0.
In Figure 2(a), one can see that beta strand is the preferable conformation for amino acid residues from -5 to -3 positions.
In our data set, the number of 3/10 helices situated near beta strands (after or before them) is almost the same as the number of 3/10 helices situated near alpha helices.
It has been shown that random coil regions can be considered to function as "connecting bridges" between major elements of secondary structure (alpha helices and beta strands) [12].
So, according to both classifications, the most of the proteins from this study contain both alpha helices and beta strands.
Four amino acid residues, known as coil formers [13] (Asp, Asn, Gly, and Pro), are used in pure random coil regions between two beta strands significantly (P < 0.05) more frequently than in connecting bridges containing 3/10 helices.
On the other hand, the appearance (by the way of mutation) of strong beta sheet formers [13] (Phe, Tyr, Ile, and Val) in the region between two beta strands may lead to the elongation of those beta strands or to the formation of additional beta strands.
According to our data, structural transitions from coil to 3/10 helix and vice versa should be frequent in regions connecting two alpha helices, alpha helices and beta strands, and beta strands and alpha helices.