Rice R H, Green H
Cell. 1977 Jun;11(2):417-22. doi: 10.1016/0092-8674(77)90059-9.
A small proportion of the protein of stratum corneum of human epidermal callus is insoluble even when boiled in solutions containing sodium dodecylsulfate and a reducing agent. This protein is present in the cornified envelope, a structure located beneath the plasma membrane. When cornified envelopes were dissolved by exhaustive proteolytic digestion and the products analyzed by chromatography, approximately 18% of the total lysine residues were found as the cross-linking dipeptide epsilon-(gamma-glutamyl) lysine. Labeled cornified envelope protein was synthesized by human epidermal keratinocytes allowed to differentiate terminally in culture. The extent of cross-linking, determined from the proportion of radioactive lysine in epsilon-(gamma-glutamyl) lysine after exhaustive proteolysis, was similar to that in stratum corneum. The properties of the cornified envelopes (insolubility in detergent and reducing agents, and solubility following proteolytic digestion) are readily explained by a structure consisting of a cross-linked protein lattice.
人表皮角质层的一小部分蛋白质即使在含有十二烷基硫酸钠和还原剂的溶液中煮沸也不溶解。这种蛋白质存在于角质包膜中，角质包膜是位于质膜下方的一种结构。当通过彻底的蛋白水解消化溶解角质包膜并通过色谱法分析产物时，发现约18%的总赖氨酸残基以交联二肽ε-(γ-谷氨酰基)赖氨酸的形式存在。标记的角质包膜蛋白由在培养中终末分化的人表皮角质形成细胞合成。通过彻底蛋白水解后ε-(γ-谷氨酰基)赖氨酸中放射性赖氨酸的比例确定的交联程度与角质层中的相似。角质包膜的特性（在去污剂和还原剂中不溶，在蛋白水解消化后可溶）很容易用由交联蛋白质晶格组成的结构来解释。
