Sulfhydryl groups, amino acid structure

It can be assumed that the amino acids following this hinge region (Val 93 to Leu 447) are part of the head domain. The point of papain cleavage is at amino acid 82 27. TTie core part of the polypeptide chain is mainly folded in )3-sheets (34 %) and to a lesser extent (15 %) arranged in alpha-helical structures 7. In contrast with CBH I the core of CBH II possesses only 2 disulfide bridges (176-235 368-415) and four free sulfhydryl groups. Similarly to CBH I carboxyl functions are involved in the active center (Asp 175 and Glu 184) 28. 

Disulfides — A disulfide bond (R-S-S-R) is a strong covalent bond formed by the oxidation of two sulfhydryl groups (R-S-H). An amino acid that commonly forms S-S bonds in proteins is cysteine. When two cysteines are bonded by an S-S bond, the resulting molecule between the two protein chains is called cystine. The presence of disulfide bonds helps to maintain the tertiary structure of the protein. Industrial production of L-cysteine is based on the electrochemical - reduction of L-cystine in acidic - electrolytes using lead or silver -> cathodes. 

Disulfide Bonds. The sulfhydryl groups of the amino acid cysteine often (but not always) form partners in intrachain or interchain disulfide bonds, and they thus serve to fix a protein molecule into a three-dimensional structure. While such bonds are,... 

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