Anti-parallel 3-sheets

Abbreviations Ala, L-alanine Leu, L-leucine Glu(OBzl), 7-benzyl L-glutamate NHBu, n-butyl amide OBzl, benzyl ester PG, polyglycine NCA, A-carboxy-a-amino acid anhydride a-helix, right-handed a-helix , 3-sheet, anti-parallel /3-sheet. 

The two peptides form a symmetrical dimer stabilized by four hydrogen bonds (red dashes) and hydrophobic contacts. The two monomers form a four-stranded, anti-parallel pleated sheet. 

We have sequenced RpII and studied the structures of RpII and RpIII in solution by 2D-NMR and distance geometry methods. The resonances are almost completely assigned, and secondary and tertiary structures have been determined. Our results indicate that Rp toxins have a four strand anti-parallel )9-sheet and no a-helix. Functionally important residues are found to be located in looped regions of the... 

It is a supposition that the )9-sheet structure of neurotoxin is an essential structural element for binding to the receptor. The presence of -sheet structure was found by Raman spectroscopic analysis of a sea snake neurotoxin (2). The amide I band and III band for Enhydrina schistosa toxin were at 1672 cm and 1242 cm" respectively. These wave numbers are characteristic for anti-parallel -sheet structure. The presence of -sheet structure found by Raman spectroscopic study was later confirmed by X-ray diffraction study on Laticauda semifasciata toxin b. 

Fig. 4.12(a). An outline structure of a protein (here the enzyme phospholipase A2), showing a-helical runs of amino acids as cylinders (A-E) and anti-parallel P-sheet runs as heavy black arrows. Disulfide cross-links are shown (the enzyme is extracellular), and runs of no a/p secondary structure appear as thin lines. The structure is relatively immobile, and binds calcium in a constrained loop. (Reproduced with permission from Professor J. Drenth.)... 

The effect of formalin-treatment on the structural properties of RNase A was examined using circular dichroism (CD) spectropolarimetry. A brief introduction to CD spectropolarimetry is provided in Section 15.15.2 for those readers unfamiliar with this biophysical method. The secondary structure of RNase A consists of one long four-stranded anti-parallel p-sheet and three short a-helixes,44 which places RNase A in the a + p structural class of proteins. The effect of a 9-day incubation of RNase A (6.5mg/mL) in 10% formalin on the protein secondary structure was examined with CD spectropolarimetry in the far-UV region (170-240nm) as shown in Figure 15.6a. The resulting... 

Arnott, S., Dover, S. D., and Elliott, A. (1967). Structure of / -poly-L-alanine Refined atomic co-ordinates for an anti-parallel /(-pleated sheet./. Mol. Biol. 30, 201-208. 

In a further exploration of the relationship between dye structure and wet fastness on silk, four novel monoazo J acid derivatives (3.169 X = Xx to X4), including 3.168 (X = X2) made from 2-aminobenzophenone, were synthesised. Silk was dyed at pH 4 and 85 °C and the dyeings tested for fastness to washing, perspiration and dry cleaning. The highest allround fastness was shown by the 4 aminobenzophenone derivative (X = X4), a structure that resembles the anti-parallel pleated sheet arrangement of polypeptide chains in silk [183]. 

Figure 4.7 (a) Parallel and (b) anti-parallel (3-sheets showing hydrogen bonds, but omitting side chains (from Voet and Voet, 2004) (c) parallel and (d) anti-parallel 3-sheets illustrating the pleated nature of the sheet. (From Branden and Tooze, 1991. Reproduced by permission of Garland Publishing, Inc.)... 

Figure 4.8 Super-secondary structures found in proteins (a) P-a-P motifs (b) anti-parallel P-sheets connected by hairpin loops (c) a-a motifs. (From Voet and Voet, 2004. Reproduced with permission from John Wiley Sons., Inc.)...

Figure 11.4 Pleated sheets of fibrous proteins. Parallel pleated sheets are composed of polypeptide chains which all have their N-terminal amino acid at the same end whereas anti-parallel pleated sheets involve polypeptide chains which are alternately reversed in direction. Both forms of sheet show a high degree of hydrogen bonding between the chains.

The first type of anti parallel /3 barrel, in analogy with the first type of helix bundle, has simple up and down +1,+ 1,+ 1 connections all around. Although it is relatively unusual for a barrel to be composed entirely of up-and-down strands, many of the larger barrels and sheets have four- to six-stranded sections of simple up-and-down topology... 

NMR characterization of the recombinant mouse,hamster, bovine and human prion proteins showed that all these molecules share a common architecture, consisting of a flexible unstructured N-terminal tail of about 100 residues from position 23 to position 124 attached to a globular domain within residues 125-228. The globular domain contains a double-stranded anti-parallel /1-sheet and three ot-helices (Fig. 6). 

Native monellin consists of two polypeptide chains, a 45-residue A-chain and a 50-residue B-chain, linked by non-covalent interactions. At neutral pH, it is fairly resistant to heat denaturation with a higher than 80 °C. The crystal structure of native monellin shows a tertiary structure comprising an anti-parallel /1-sheet with five strands and an a-helix. H NMR spectroscopy and hydrogen exchange methods have been used to characterize the alcohol-denaturated state of monellin in order to understand how its secondary structure depends on environmental conditions. " Structural and dynamic studies by NMR have been carried out in order to compare native monellin and a non-sweet analogue in which Asp was replaced by Abu . The three-dimensional structures of the two proteins are found to be very... 

R 6 H R 6 H R OHROHROH 1 II II 1 II II anti-parallel p-sheet carbonyl to amino peptide linkages in opposite directions H... 

Crystal structure(s) of ACTH-(1-39) or 1-24 are not known. Suitable crystals for X-ray diffraction experiments could be obtained however, for the heptapeptide 4-10 (54, 55) and the smaller tetrapeptide 4-7 (54, 56). In the former case, an anti--parallel p-pleated sheet structure of the backbone was found with clustering of hydrophobic (Met, PheandTrp) and hydrophilic (Glu, His, Arg) side-chains as remarkable features. ACTH-(4-7)... 

X-ray diffraction analysis reveals the 3-D structure of both IL-1 molecules to be quite similar. Both are globular proteins, composed of six strands of anti-parallel jS-pleated sheet forming a barrel , which is closed at one end by a further series of jS-sheets. 

Monomeric TNF is biologically inactive — the active form is a homotrimer in which the three monomers associate non-covalently about a three-fold axis of symmetry, forming a compact bell-shaped structure. X-ray crystallographic studies reveal that each monomer is elongated and characterized by a large content of anti-parallel /1-pleated sheet, which closely resembles subunit proteins of many viral caspids (Figure 5.10). 

For an octapeptide sequence taken from the C-terminal residues of the Alzheimer s Ap-peptide Lansbury et al. identified a large intensity enhancement for 13C-labeled modes that was sequence-dependent and assessed as largely due to interstrand dipole-coupling.1207,2351 Mendelsohn et al. found a similar effect by double labeling on alternate sites a peptide that formed a P-sheet-like structure in methanol.12501 Subsequent theoretical modeling showed this latter intensity enhancement to be a function of forming extended, flat, anti-parallel P-sheet structures,12511 and the overall effect to be highly position sensitive.12451... 

This structure, because of the anti parallel packing, gives rise to alternate 3.5 and 5.7 A spacings between layers, repeating many times over, in the plane of the sheet. The arrangement is shown in Figure 14.3. 

Structural modelling of PG and PLV with the anti-parallel P-sheet form 43... 

Further, a molecular model for the anti-parallel (3-sheet conformation of PG and PLV have been calculated using the X-PLOR 3.1 program, and we have measured carbon-proton distances from the modeled structure. 

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