Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.64 (proteinase K)
 4,071 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cornified cell envelope (CE) is a 15-nm thick layer of insoluble protein deposited on the intracellular side of the cell membrane of terminally differentiated stratified squamous epithelia. The CE is thought to consist of a complex amalgam of proteins cross-linked by isodipeptide bonds formed by the action of transglutaminases, but little is known about how or in which order the several putative proteins are cross-linked together. In this paper, CEs purified from human foreskin epidermis were digested in two steps by proteinase K, which released as soluble peptides about 30% and then another 35% of CE protein mass, corresponding to approximately the outer third (cytoplasmic surface) and middle third, respectively. Following fractionation, 145 unique peptides containing two or more sequences cross-linked by isodipeptide bond(s) were sequenced. Based on these data, most (94% molar mass) of the outer third of CE structure consists of intra- and interchain cross-linked loricrin, admixed with SPR1 and SPR2 proteins as bridging cross-links between loricrin. Likewise, the middle third of CE structure consists largely of cross-linked loricrin and SPR proteins, but is mixed with the novel protein elafin which also forms cross-bridges between loricrin. In addition, cross-links involving loricrin and keratins 1, 2e, and 10 or filaggrin were recovered in both levels. The data establish for the first time that these several proteins are indeed cross-linked protein components of the CE structure. In addition, the data support a model for the intermediate to final stages of CE assembly: the proteins elafin, SPR1 and SPR2, and loricrin begin to be deposited on a preformed scaffold; later, elafin deposition decreases as loricrin and SPR accumulation continues to effect final assembly. The recovery of cross-links involving keratins further suggests that the subjacent cytoplasmic keratin intermediate filament-filaggrin network is anchored to the developing CE during these events.
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PMID:The proteins elafin, filaggrin, keratin intermediate filaments, loricrin, and small proline-rich proteins 1 and 2 are isodipeptide cross-linked components of the human epidermal cornified cell envelope. 754 90

The cornified envelope (CE) is an insoluble sheath of epsilon-(gamma-glutamyl)lysine cross-linked protein, which is deposited beneath the plasma membrane during keratinocyte terminal differentiation. We have probed the structure of the CE by proteolytic cleavage of purified CE fragments isolated from CEs formed spontaneously in cell culture. CNBr digestion, followed by trypsin and then proteinase K treatment released 25%, 42%, and 18%, respectively, of the CE protein. Purification and sequencing of released peptides has identified two novel CE precursors, S100A11 (S100C, calgizzarin) and S100A10 (calpactin light chain). We also sequenced peptides derived from annexin I and plasminogen activator inhibitor 2, two putative envelope precursors, as well as portions of the well established CE precursor proteins SPR1A, SPR1B, and involucrin. Many desmosomal components were identified (desmoglein 3, desmocolin A/B, desmoplakin I, plakoglobin, and plakophilin), indicating that desmosomes become cross-linked into the CE. Fragments derived from envoplakin, the recently sequenced 210-kDa membranous CE precursor protein, which also appears to be a desmosomal component, were also identified. Analysis of the pattern of peptide release following the sequential digestion indicates that S100A11 is anchored to the envelope via Gln102 and/or Lys103 at the carboxyl terminus and at Lys3, Lys23, and/or Gln22 in the amino terminus. A similar type of analysis indicates that small proline-rich proteins 1A and 1B (SPR1A and SPR1B) become cross-linked at the amino terminus (residues 1-23) and the carboxyl terminus (residues 86-89). No loricrin, cystatin A, or elafin peptides were detected.
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PMID:S100A11, S100A10, annexin I, desmosomal proteins, small proline-rich proteins, plasminogen activator inhibitor-2, and involucrin are components of the cornified envelope of cultured human epidermal keratinocytes. 911 70