Nutrition Guide

Type II keratins (or Type II cytokeratins) constitutes the Type II intermediate filaments (IFs) of the intracytoplasmatic cytoskeleton, which is present in all mammalian epithelial cells. The type 2 cytokeratins consist of basic or neutral, high molecular weight proteins which in vivo are arranged in pairs of heterotypic Type I and Type II keratin chains, coexpressed during differentiation of simple and stratified epithelial tissues.

Type II cytokeratins are encoded on chromosome 12q and encompasses: CK1, CK2, CK3, CK4, CK5, CK6, CK7 and CK8. Their molecular weight ranges from 52 kDa (CK8) to 67 kDa (CK18).

Type II hair keratin is one of the two types of hair keratin. It is a basic protein which heterodimerizes with type I hair keratins to form hair and nails.

Type I keratins (or Type I cytokeratins) constitutes the Type I intermediate filaments (IFs) of the intracytoplasmatic cytoskeleton, which is present in all mammalian epithelial cells. Most of the type I cytokeratins consist of acidic, low molecular weight proteins which in vivo are arranged in pairs of heterotypic Type I and Type II keratin chains, coexpressed during differentiation of simple and stratified epithelial tissues.

Type I cytokeratins are encoded on chromosome 17q and encompasses: CK9, CK10, CK11, CK12, CK13, CK14, CK15, CK16, CK17, CK18, CK19 and CK20. Their molecular weight ranges from 40 kDa (CK19) to 64 kDa (CK9).

Keratin 9 is a type I cytokeratin. It is found only in the terminally differentiated epidermis of palms and soles. Mutations in the gene encoding this protein cause epidermolytic palmoplantar keratoderma.

Antibodies to CK8 (e.g. CAM 5.2) can be used to differentiate lobular carcinoma of the breast from ductal carincoma of the breast.[1]

Keratin 8, also cytokeratin 8 and CK8, is a keratin protein. It is often paired with keratin 18.

Keratin 7, also known as KRT7, is a human gene.[1]

Keratin 7 is a member of the keratin family. It is specifically expressed in the simple epithelia lining the cavities of the internal organs and in the gland ducts and blood vessels.

The protein encoded by this gene is a member of the keratin gene family. The type II cytokeratins consist of basic or neutral proteins which are arranged in pairs of heterotypic keratin chains coexpressed during differentiation of simple and stratified epithelial tissues. This type II cytokeratin is specifically expressed in the simple epithelia lining the cavities of the internal organs and in the gland ducts and blood vessels. The genes encoding the type II cytokeratins are clustered in a region of chromosome 12q12-q13. Alternative splicing may result in several transcript variants; however, not all variants have been fully described.[1]

At the present time, no mutations have been reported in this keratin gene in relation to human genetic skin diseases.

Like the closely related KRT6A and KRT6B genes, the KRT6C gene consists of 9 exons separated by 8 introns and is located in the type II keratin gene cluster on human chromosome 12q. Keratin 6A and keratin 6B are encoded by the neighbouring genes, which are identical in intron-exon organization to KRT6C and are more than 99% identical in their DNA coding sequences.

Keratins are the intermediate filament proteins that form a dense meshwork of filaments throughout the cytoplasm of epithelial cells[1]. Keratins form heteropolymers consisting of a type I and a type II keratin. Keratins are generally expressed in particular pairs of type I and type II keratin proteins in a tissue-specific and cellular differentiation-specific manner.

The keratin proteins of epithelial tissues are commonly known as “keratins” or are sometimes referred to as “epithelial keratins” or “cytokeratins”. The specialized keratins of hair and nail are known as “hard keratins” or “trichocyte keratins”. Trichocytes are the specialized epithelial cells from which hair and nail are composed. Trichocyte keratins are similar in their gene and protein structure to keratins except that they are especially rich in the sulfur-containing amino acid cysteine, which facilitates chemical cross-linking of the assembled hard keratins to form a more structurally resilient material.

Both epithelial keratins and hard keratins can be further subdivided into type I (acidic) keratins and type II (neutral-basic) keratins. The genes for the type I keratins are located in a gene cluster on human chromosome 17q, whereas the genes for type II keratins are located in a cluster on human chromosome 12q (the exception being K18, a type I keratin located in the type II gene cluster).