|Protein Name||Keratin, type I cytoskeletal 17|
|Ref Sequence Id||NP_001098792.1|
|Amino Acid Lenth||441|
|Protein Existence Status||Reviewed: Experimental evidence at transcript level|
|Presence in other biological fluids/tissue/cells||expressed in epithelial cells|
|Protein Function||Keratins—types I and II—are the intermediate-filament (IF)-forming proteins; one of the primary roles of keratin filaments is to provide structural support; resist chemical stresses and assist the cell in maintaining a polarized cytoarchitecture; contribute to the mechanical resilience;|
|Biochemical Properties||pI range is 4.5 to 9.5; type I keratin proteins tend to be smaller (40–56.5 kDa) and acidic in overall charge (pI 4.5–6.0), whereas type II keratins are larger (50–70 kDa) and basic-neutral in charge (pI 6.5–8.5); Types I and II keratins are strictly interdependent for assembly into 10-nm filaments, initially forming coiled-coil heterodimers at the very first stage of the process; Keratin dimers and even tetramers can form under very harsh denaturing conditions,signifying unusual strength of the interactions between type I and type II keratins; Keratin monomers appear very unstable in most biological settings, whereas keratin assemblies are more stable but can undergo rapid turnover and/or be remodeled depending on the circumstances of the cell such as mitosis;|
|Significance in milk||Keratin from teat canal lining represent the homogeneous populations of luminal epithelial cells from milk|
|PTMs||undergo several posttranslational modifications (PTMs), including phosphorylation, O-linked glycosylation, ubiquitination, acetylation, SUMOylation, and transamidation; known keratin phosphorylation sites are serine/threonine residues that are located in the head and tail domains of the keratins; glycosylation of keratins also occurs on serine residues|
|Significance of PTMs||function of keratin phosphorylation is to enhance keratin solubility, which in turn triggers reorganization of the keratin filament network; keratin phosphorylation provides cytoprotection by iserving as a phosphate sponge which shunt undesirable phosphorylation of proapoptotic proteins; Keratin glycosylation appears to modulate the K8–K18 signaling scaffold; Keratin SUMOylation is barely detectable under basal conditions but is markedly enhanced during apoptosis, exposure to oxidative stress, phosphatase inhibition; ubiquitination is crucial for the turnover of keratins by the proteasome, which occurs during proteotoxic stress;|
|Bibliography||1. Ku, N.-O., Michie, S., Resurreccion, E. Z., Broome, R. L., & Omary, M. B. (2002). Keratin binding to 14-3-3 proteins modulates keratin filaments and hepatocyte mitotic progression. Proceedings of the National Academy of Sciences of the United States of America, 99(7), 4373–4378. https://doi.org/10.1073/pnas.072624299. |
2. Smolenski, G. A., Cursons, R. T., Hine, B. C., & Wheeler, T. T. (2015). Keratin and S100 calcium-binding proteins are major constituents of the bovine teat canal lining. Veterinary Research, 46(1). https://doi.org/10.1186/s13567-015-0227-7.
3. Taylor-Papadimitriou, J., Stampfer, M., Bartek, J., Lewis, A., Boshell, M., Lane, E. B., & Leigh, I. M. (1989). Keratin expression in human mammary epithelial cells cultured from normal and malignant tissue: relation to in vivo phenotypes and influence of medium. Journal of Cell Science, 94 ( Pt 3), 403–413. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/2483723.
4. Snider, N. T., & Omary, M. B. (2014, March). Post-translational modifications of intermediate filament proteins: Mechanisms and functions. Nature Reviews Molecular Cell Biology, Vol. 15, pp. 163–177. https://doi.org/10.1038/nrm3753.
5. Kim, S., & Coulombe, P. A. (2007). Intermediate filament scaffolds fulfill mechanical, organizational, and signaling functions in the cytoplasm. Genes & Development, 21(13), 1581–1597. https://doi.org/10.1101/gad.1552107.
6. Moll, R., Franke, W. W., Schiller, D. L., Geiger, B., & Krepler, R. (1982). The catalog of human cytokeratins: Patterns of expression in normal epithelia, tumors and cultured cells. Cell, Vol. 31, pp. 11–24. https://doi.org/10.1016/0092-8674(82)90400-7