1.Evidence for a cysteine-histidine thioether bridge in functional units of molluscan haemocyanins and location of the disulfide bridges in functional units d and g of the betaC-haemocyanin of Helix pomatia.
Gielens C1, De Geest N, Xin XQ, Devreese B, Van Beeumen J, Préaux G. Eur J Biochem. 1997 Sep 15;248(3):879-88.
In functional units d and g from the betaC-haemocyanin of the gastropod Helix pomatia, aminoacid analysis in the presence of dimethyl sulfoxide showed the occurrence of seven cysteine residues. Titration with 5,5'-dithiobis(2-nitrobenzoic acid), however, did not reveal any free thiol group. Pepsinolysis at pH 2.0 followed by amino acid analysis and partial sequencing of the cysteine-containing peptides showed that six cysteine residues are involved in the formation of three disulfide bridges at corresponding positions. The results indicated that the remaining cysteine residue is linked by a thioether bridge to a histidine residue located two positions further in the sequence (H. pomatia d Cys60 His62; H. pomatia g Cys66 His68). This residue corresponds to one of the three histidine residues considered to be involved in the coordination of the copper A atom of the dinuclear copper group of the functional units. The presence of the thioether bond was further evidenced by an absorption band at 255 nm and by molecular mass determinations with electrospray mass spectrometry on a peptic peptide from H.
2.A new synthesis of 2-thiolhistidine together with experiments towards the synthesis of ergothioneine.
Harington CR1, Overhoff J. Biochem J. 1933;27(2):338-44.
3.Note on the electrometric titration of dl-2-thiolhistidine.
Richardson GM1. Biochem J. 1933;27(4):1036-9.
4.Oxidation, photosensitized by certain diketones, of enzymes and protection against such oxidation by histidine derivatives.
Mäkinen KK, Mäkinen PL. Biosci Rep. 1982 Mar;2(3):169-75.
Bovine milk lactoperoxidase, eel acetylcholinesterase, and Aeromonas aminopeptidase were photooxidized and inactivated in broad-spectrum visible light in the presence of 2,3-butanedione and 1-phenyl-1,2-propanedione. Methylglyoxal caused similar effects at 254 nm. 2-Thiol-L-histidine and 3-methyl-L-histidine protected the enzymes against photoinactivation more effectively then N3-, even at a molar ratio of 2:1 (protector to enzyme). These compounds also delayed the photoinactivation of acetylcholinesterase, induced by ultraviolet light.