CELL MEMBRANE COMPLEX 453 loricrin and involucrin are most likely in the cellular envelopes of wool (CE wool) and thus of human hair (CE hair) and other animal hairs. Loricrin is the major component (60% to 80%) of the cornifi ed cell envelope of stratum corneum in most animals, and involucrin, which is rich in glutamine, has an almost ideal structure to provide cross- linking sites to other proteins via isopeptide bonds. Therefore, involucrin is likely a major component of the cuticle cell membrane. Isopeptide bonds are formed between glutamine and lysine, reacting in the presence of a transglutaminase enzyme similar to what Steinert and Marekov (68) have shown occurs in the cellular envelope of human skin. Exactly how these proteins might be arranged in the cuticle cell membranes is not known at this time. One reasonable conjecture is that two layers exist in the epicuticle, the outermost (upper) layer being comprised primarily of UHSP to provide anchoring sites for 18-MEA on the top portion of the membrane and also covalent anchoring sites for other fatty acids on the bottom part of epicuticle cells. Involucrin is likely interspersed in the UHSP to provide isopeptide crosslinks to it and also to loricin and other proteins in the second layer of the cuticle cell membrane. Zahn et al. (31) also pointed out that small proline-rich proteins (SPRP) that are rich in glu- tamine and lysine are also most likely a part of this membrane because SPRPs (70) have been shown to participate in isopeptide cross-linking in the CE of stratum corneum and Table III Amino Acids (in mole%) of Allworden Membrane vs Calculated Values for Wool CE by Zahn et al. (31) and Proteins Believed to Be Part of This Membrane Amino acids Wool CE Human loricrin Human involucrin Human UHSP Human SPRP Allworden membrane Asp 2.7 0.3 2.8 3.4 0 3 Glu 9.8 4.4 45.8 8.2 28 8.6 Thr 2.2 2.2 1.6 10.3 2.4 2.1 Ser 15 22.8 1.6 10.9 0.4 14.3 Tyr 0.2 2.5 0.8 1 0 0 Pro 4 2.9 5.7 9 31.2 4.2 Gly 24.5 46.8 6.7 5 0 23.8 Ala 3.2 1 1.5 1.4 0 3.2 Val 3.5 3.5 3.7 3.8 9.6 5.6 Iso 1.1 1.6 0.4 1.6 0 1.2 Leu 2.4 0 14.6 2.4 1.6 2.9 Trp 0 0.3 0 0 0 Phe 0.8 2.9 0.6 0.8 0 0.4 His 0.9 0.3 4.7 0.7 0.8 0.2 Lys 5.3 2.2 7.4 3.7 12. 8 4.5 Arg 1.7 0 0.7 5.6 0 2.5 Met 0 0 0.9 0 0 0 Cys 22.7 6 0.3 32.2 11.2 21.1 Totals 100 99.7 99.8 100 98 97.6 Wool CE calculated by Zahn et al. (31). Human loricin from Hohl et al. (64). Human involucrin from Eckert and Green (65). Human SPRP from Marvin et al. (66). Human UHSP from Tezuka and Takahashi (67). Allworden membrane by Allen et al. (30).

JOURNAL OF COSMETIC SCIENCE 454 because we know that isopeptide bonding is critical to the chemical resistance (attack by oxidizing and reducing agents) displayed by these membranes in human hair and wool fi ber in the Allworden reaction and other reactions. Thus, the stability and resistance to chemical attack by this membranous material is provided through two types of cross- links: cystine crosslinks (vulnerable to oxidizing and reducing agents) and isopeptide crosslinks that are resistant to oxidizing and reducing agents. PROTEINS IN THE CORTICAL CELL MEMBRANES Proteinaceous material called “resistant membranes” have been isolated from both the oxidation of wool and/or hair with performic or peracetic acid followed by treatment with either ammonia or alkaline urea (71). The authors of this paper state that this material from the performic acid reaction is similar to that of their own analysis of the Allworden membrane nevertheless, it is clearly different from the Allworden membrane analysis by Allen et al. (30) as summarized in Table IV. Treatment of keratin fi bers with either peracetic or performic acids and separation into three fractions according to solubilities has been called the “keratose” method by Alexander and Earland (72). After oxidation, adjustment of the pH to the alkaline side provides an insoluble fraction called beta-keratose, about 10% of the weight of the hair. Acidifi ca- tion to pH 4 provides a fraction greater than 50%, called alpha-keratose, containing crystalline material, by X-ray diffraction, and the third fraction is called gamma-keratose. The beta-keratose fraction is believed to be proteins derived primarily from cell mem- brane material however, other proteins are likely to be present. According to a different workup procedure by Bradbury et al. (71), only 1–1.55% residue is provided. Other workup procedures have been applied to the keratose method (73). Table IV Allen’s (30) Analysis of the Allworden Membrane vs Resistant Membranes from Performic Acid Reaction with Wool Fiber (71) Amino acids Allworden membrane (30) Resistant membranes (71) Asp 3 5.4 Glu 8.6 10.3 Thr 2.1 5.7 Ser 14.3 10 Tyr 0 0 Pro 4.2 7.1 Gly 23.8 14.2 Ala 3.2 6.5 Val 5.6 4.9 Iso 1.2 2.6 Leu 2.9 4.9 Trp — 0 Phe 0.4 1.5 His 0.2 1.3 Lys 4.5 8.4 Arg 2.5 4.2 Met 0 0 Cys 21.1 13 Totals 97.6 100