High-sulfur proteins

Figure 8.5 CZE profiles (pH 9.2) of the retained (A) and unretained (B) fractions obtained after passing the crude extract through Bio-Rad AG 50W-X8 filter, and of proteins retained on the cation-exchange cartridge from the alcohol-treated rat hair preparation (C). High-sulfur proteins were recovered in the filtrate, while low-sulfur proteins were released by 0.1 M triethylamine. Comparison with the two-dimensional gel separations is visualized under each CZE run. The position of the fraction of low-sulfur proteins occurring in alcohol-treated animals but absent in controls is indicated by an arrow. (From Jelfnkov et al., 1995, with permission.)...

This preparation can be freed of traces of high-sulfur proteins by precipitation at pH 6.0 with zinc acetate (Gillespie, 1957) or by acidification to pH 4.4 in the presence of 0.3-0.5 M KCl (Gillespie ei al., 1962). The zinc ions can be removed by dialysis against citrate (Gillespie and Springell, 1957). 

Unlike the low-sulfur proteins the high-sulfur proteins SCMKBl and SCMKB2 behave as random coils in aqueous solution and very little a-helix structure is formed even when they are dissolved in the helix-favoring solvent 2-chloroethanol (Gillespie, 1962b Gillespie and Harrap, 1963). Absence of a-helix structure in the high-sulfur proteins is consistent with their location in the amorphous matrix of the wool fiber. 

Table XI also compares the amino acid analyses of Merino 64 s wool with that of cuticle obtained by subjecting the wool to ultrasonic irradiation in 98 % formic acid (Bradbury and Chapman, 1964). The cuticle contained less arginine, aspartic acid, glutamic acid, leucine, and phenylalanine than whole wool, but more cystine, proline, serine, and valine. Cys-teic acid is probably formed during the ultrasonic treatment. These analyses cannot be accounted for quantitatively on the basis of a simple combination of low-sulfur and high-sulfur protein fractions, but the data suggest that the cuticle would not contain as much material in the a-helical conformation as the original fiber. The values obtained by Bradbury (1960) in an earlier examination of cuticle-rich material obtained by a mechanical descaling technique are in reasonable agreement with the values in Table XI.

It would appear that the follicle cells produ( e a range of high-sulfur proteins that vary in relative amount according to the availability of cystine and possibly other amino aedds. 

Increase the cysteine and methionine amino acids (high sulfur protein) in alfalfa. This is being attempted by Australian scientists by inserting pea genes (p-albumin-1) into alfalfa, anticipating enhanced wool production in sheep... 

These relationships are based on the fact that leucine and cystine are common components of the low-sulfur proteins and that proline and cystine are primary components of the high-sulfur proteins. They further suggest that the cystine content should be about 17 to 18% and that large variations beyond the calculated values for these three amino acids indicate some cause of variation such as genetic, environmental (sunlight exposure), cosmetic treatment, or diet. Variation from these factors is described later. 

By analogy with the effects of malnutrition and sulfur enrichment on the high-sulfur proteins of the keratin-associated proteins in wool fiber [44,45], these effects of a lower cystine content in hair are probably a result of a decreased synthesis of the sulfur-rich proteins because of malnutrition. Studies of the effects of diet in persons suffering malnutrition (i.e., protein deficiencies) show that diet supplementation can influence the protein composition of human hair. However, such effects have only been demonstrated among persons suffering from severe malnutrition and never among healthy persons on a normal diet see the section on the keratin-associated proteins of human hair later in this chapter. 

HS, high-sulfur proteins UHS, ultra high sulfur proteins... 

Amino Acid Sequences of High-Sulfur Proteins.354... 

Methods for isolating cuticle cells from wool fibers have been described by Ley and Crewther [90]. After using alkaline reducing conditions for the extraction of cuticle cell polypeptides, they were able to solubilize about 30% w/w of the cells and suggested that the aforementioned isopeptide bonds would account for low yields. In amino acid and electrophoretic studies, these isolated polypeptides were cystine-rich but clearly different from cortical cell high-sulfur proteins [91]. 

---