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Background: TgMIC4 is an important microneme effector protein from Toxoplasma gondii. Results: The structure of TgMIC4 together with carbohydrate microarray analyses reveal a broad specificity for galactoseterminating sequences. Conclusion: Lectin activity within the fifth apple domain of TgMIC4 is reminiscent of the mammalian galectin family. Significance: TgMIC4 may contribute to parasite dissemination within the host or down-regulation of the immune response.

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a b s t r a c tSunflower Trypsin Inhibitor (SFTI-1) analogues have been prepared from simple linear precursors produced either by chemical synthesis or following purification from Escherichia coli. We have shown, for the first time that these linear SFTI-1 derived peptide sequences can be converted to circular peptides via selective consecutive acyl transfer reactions, and that the products derived from synthetic and bacterial origin are identical. Preliminary analysis of the semi-synthetic SFTI-1 analogues confirmed SFTI-I10H as an inhibitor of Kallikrein-5 (KLK5) protease that could also mediate its action on human keratinocytes. The preliminary results obtained serve as a useful starting point for the biological production of SFTI-1 based, selective KLK5 inhibitors for the treatment of atopic dermatitis.

Tagging the terminus: N→S acyl transfer in native peptides and proteins can be reliably intercepted with hydrazine. The method allows selective labeling and ligation, without recourse to the use of protein‐splicing elements. NCL=native chemical ligation.

3/4-Mercaptobenzyl sulfonates were investigated as aryl thiol catalysts for native chemical ligation (NCL). Whilst catalysing NCL processes at a similar rate to 4-mercaptophenyl acetic acid (MPAA), the increased polarity and solubility of 3-mercaptobenzyl sulfonate in particular may favour its selection as NCL catalyst in many instances.

Shortly preceding the submission of this manuscript, a paper by Müller et al. (Müller, J. J., Weiss, M. S., and Heinemann U. (2011) Acta Crystallogr. D 67, 936 -944) revealed the crystal structure of the Sarcocystis muris TgMIC4 homolog SML-2 in complex with 1-thio-␤-Dgalactose. This structure demonstrates that SML-2 binds to galactose via the same mode as demonstrated for TgMIC4-A5 in this manuscript, thereby superseding our prediction of a similar binding mode here. However, it should be noted that Müller et al. suggest that a H57Y substitution in TgMIC4-A5 decreases specificity for galactose and enables incorporation of a wider range of receptors, including N-acetylglucosamine. However, we have demonstrated here that TgMIC4-A5 binds with high specificity to galactose and is incapable of adhering to glucose or its derivatives.

Recombinant, human, erythropoietin (rhEPO) is a glycoprotein hormone which is prescribed throughout the world to treat anaemia caused by chronic kidney disease or chemotherapy. rhEPO is at the forefront of the recent emergence of biosimilar medicines, with numerous products now available worldwide. Due to its complex glycosylation profile, which has a crucial influence upon biological activity, therapeutic rhEPO preparations must be closely monitored to ensure consistency, safety and efficacy. Here, we have compared twelve rhEPO preparations from eleven manufacturers in China and one in Japan, measuring in vivo biological activity and exploring its relationship with glycosylation through sialic acid content determination, isoform distribution via capillary electrophoresis (CE), O-glycan profiling, and N-glycan mapping using a novel anion-exchange/hydrophilic interaction chromatography-mass spectrometry (AEX/HILIC-MS) approach. We observed differences between glycosylation profiles, including the varying occurrence of sialic acid O-acetylation, extension of N-glycan antennae with N-acetyllactosamine units, and the distribution of sialic acids across multi-antennary structures. The presence of unusually high levels of suspected penta- and hexa-anionic N-glycans in several samples is consistent with elevated rhEPO isoform acidity, which is reflected by slightly elevated in vivo bioactivities. This aside, the observed differences in glycosylation profile do not appear to have a significant influence upon biological activity in mice. Nonetheless, with the continued emergence of biosimilars, the study highlights the importance of monitoring glycosylation profiles in biological medicines, in order to detect and account for divergence between products, as well as the presence of unusual or unexpected glycans.