A Further Study on the Extraction of Reduced Proteins From Wool

The oc-helix-rich particle produced bychymotryptic digestion of the reduced and alkylated microfibrillar proteins of wool was characterized by physicochemical methods. The preparations were homogeneous with respect to size and the particle molecular weight was found to be 50200 ± 2 000.Hydrodynamic methods indicated a length of about 20 nm for the particle. The properties of the particle, derived from two methods of isolation of the microfibrillar proteins, were identical and were also independent of the type of wool used. From a consideration of the molecular weight in denaturing solvents and from cross-linking experiments with dimethyl suberimidate a four-chain structure, consisting of a pair of double-stranded oc-helices, is proposed for the particle.

Section: Preparation Of Scmkamentioning

confidence: 99%

Structural Studies on the Microfibrillar Proteins of Wool: Characterization of the a-Helix-Rich Particle Produced by Chymotryptic Digestion

Woods¹,

Gruen²

1981

“…Samples of wool clipped at day 11 post-infusion from the patches of 12 ewes (three per flock per intake level) were reduced in urea-thioglycollate at pH 11 and separated into high-and low-sulphur protein fractions (Harrap and Gillespie 1963) with purification of the low-sulphur fraction by re-precipitation (Downes et al 1966). The high-sulphur proteins were precipitated with trichloroacetic acid.…”

Section: (D) 85s Activity In High-and Low-sulphur Proteins Extracted/mentioning

confidence: 99%

Metabolism of Cystine by Merino Sheep Genetically Different in Wool Production III. the Incorporation of Radioactivity Into Wool Fibres During and After Intravenous Infusions of l-[35S]Cystine and its Relationship to Wool Growth and Efficiency of Conversi

Williams¹

1973

Twelve mature ewes from a flock selected for high clean fleece weight (Fleece Plus) and twelve from a flock selected for low clean fleece weight (Fleece Minus) were randomly divided between two dietary treatments: 500 or 1100 g per day of chaffed lucerne hay. After the sheep experienced these dietary regimes for 40 days, each ewe was infused intravenously with L-[35Sjcystine for 12-14 hr. Incorporation of 35S activity into fibres during the infusions, and into wool clipped subsequent to the infusions, was measured.During the final 7-9 hr of infusion, the 35S activity in plucked fibres increased linearly with time. The linear regression coefficients relating 35S activity to time did not differ in the genetic or the dietary comparisons, regardless of whether the rate of incorporation of 35S was expressed relative to a 1000 fibres, or to the number of fibres growing from unit area of skin. The mean specific radioactivity of cystine incorporated into wool proteins during the infusions was less in ewes consuming 1100 g per day of lucerne (23 v. 35 nCi/mg : P < 0'05). This difference was less than the difference in the "plateau" specific radioactivity of cystine in the plasma, indicating that the 35S was differentially diluted with "cold" cystine during its transfer from plasma into the wool fibre; dilution being greater in ewes consuming the lesser quantity of feed (4, 0 v. 2·9 :A similar effect of feeding level was evident on the specific radioactivity of cystine in wool clipped from the ewes subsequent to the infusions. In addition, the specific radioactivity of cystine in wool from Fleece Plus ewes was less than that from Fleece Minus ewes (3, 2 v. 3· 6 nCi/mg : P < O· 05), indicating that greater dilution of 35S with "cold" cystine was occurring in these ewes. As judged by the wool production per unit area of skin, the efficiency of conversion of food to wool would have been greater in Fleece Plus ewes and in those consuming 500 g per day of lucerne. Thus, mechanisms controlling the dilution 0[35S between plasma and fibre, presumably arising

“…2) is consistent with a random-coil configuration (Gillespie 1962;Gillespie and Harrap 1963). Conversely, the low-sulphur proteins, which are less readily degraded, are partly helical (Harrap 1963). Other factors, however, could contribute towards the observed difference between these two proteins.…”

Section: * For Details Of Preparation See Legend To Figure 2 and Sectmentioning

confidence: 75%

Proteolysis of Wool and its S-Carboxymethyl Derivatives by Pronase and Other Proteases

Springell¹

1963

SummaryThe proteolysis of native Merino wool by pronase, a protease from Streptomyces griMm, was shown to resemble that of other proteases in liberating cortioal cells and solubilizing less than 20% of the fibre.The action of proteases on fully reduced and alkylated wool and on soluble wool proteins was compared. Modified whole wool was digested most rapidly by pronase and the least readily by pepsin. (3.4.4.1). High.sulphur proteins extracted from wool were broken down by pepsin initially at least 10 times faster than the low-sulphur proteins. The structural significance is discussed.An attempt was made to determine whether peptide bonds in the vicinity of the more readily reducible disulphide bonds were the most susceptible to proteolysis. Varying proportions of the carboxymethyl groups of fully reduced and alkylated preparations were labelled with 14C. The release of trichloroacetic acid-soluble 14C and nitrogen was measured after varying periods of incubation with proteases. The rate of liberation of 14C from modified whole wool by pronase and trypsin (3.4.4.4) was independent of the proportion of 14C present in the preparations. With pepsin, the 14C release was variable, but the ratio of percentage 14C release to percentage nitrogen release was constant and thus not related to the proportion of labelled S·carboxymethyl groups present. The rate of production of 14C soluble in trichloroacetic acid from the high-sulphur proteins was also independent of the proportion of 14C label present. The more easily reducible portion of the low-sulphur proteins appeared to be somewhat more resistant to proteolysis than the rest of the molecule, but when the nitrogen liberation was taken into account, a lack of dependence on the 14C content could once again be demonstrated.These and other findings are consistent with a random distribution of the more easily reducible disulpbide bonds in the wool fibre.