Structure of synthetic peptide analogues of an eggshell protein of Schistosoma mansoni

Abstract

The peptide (Gly-L-Tyr-L-Asp-L-Lys-L-Tyr),, referred to as F4-6, was synthesized as a model for a schistosome eggshell protein in which the Gly-Tyr-Asp-Lys-Tyr consensus sequence is repeated over 40 times. Analysis by CD, Fourier transform infrared spectroscopy, potentiometric and spectrophotometric titrations, NMR, and molecular modeling suggests that F4-6 forms some type of left-handed structure. A likely possibility appears to be a lefthanded a-helix stabilized by Lysj-Aspj+, salt bridges and possibly Aspj-Tyrj+, hydrogen bonding and Tyr-Tyr interactions. Spectroscopic studies of a number of F4-6 analogues support this conclusion. For example, substitution of D-Ala for Gly produces a peptide with enhanced left-handed helical spectral characteristics, whereas an L-Ala substitution results in a peptide with minimal structure. These studies suggest that the F4 protein from Schistosoma mansoni may be the first example of a naturally occurring protein devoid of proline and carbohydrate that forms a left-handed helix composed of L-amino acids, although alternative forms of other left-handed structures have yet to be rigorously excluded.Keywords: F4-6 peptide; Schistosoma mansoni; schistosome eggshell protein The pathology of schistosomiasis is due to the inflammatory response to the eggs of the parasitic trematode, Schistosoma mansoni (or other closely related schistosomes) lodged in the hosts' body tissues. Granulomas form around the eggs in response to soluble carbohydrate and protein antigens secreted by the eggs. When an egg is deposited by the female schistosome, it contains a fertilized ovum and 30-40 vitelline cells. Development of the miracidium larva occurs inside the eggshell lodged in the host tissues. The eggshell is formed shortly before egg laying from protein precursors secreted by the vitelline cells that subsequently become surrounded by the eggshell. These vitelline cells serve as a food supply for the developing miracidium and disappear before hatching. The secreted

Structure and reorientational dynamics of angiotensin I and II: a microscopic physical insight

“…Histidine(s) a (Å) Water Na + Cl À Atoms ANGIn Neutral 36 1446 4 4 4528 ANGIp Protonated 36 1445 3 5 4527 ANGIIn Neutral 32 996 3 3 3140 ANGIIp Protonated 32 997 2 3 3143 nent of AngII at both pH's resembles that of a left-handed α-helix (Middaugh et al, 1993;Mortishire-Smith, Drake, Nutkins, & Williams, 1991). Peak positions of AngII, pH 4.8 are slightly shifted to higher wavelengths according to SVD analysis; however experimental data ( Figure 2C) at low temperatures (263-283 K) contain peaks that possibly more closely resemble a left-handed helical signature.…”