Abstract
Glycine is an amino acid with unique properties because its side chain is composed of a single hydrogen atom. It confers conformational flexibility to proteins and conserved glycines are often indicative of protein domains involving tight turns or bends. All six beta-type connexins expressed in human epidermis (Cx26, Cx30, Cx30.3, Cx31, Cx31.1 and Cx32) contain a glycine at position 12 (G12). G12 is located about halfway through the cytoplasmic amino terminus and substitutions alter connexin function in a variety of ways, in some cases altering protein interactions and leading to cell death. There is also evidence that alteration of G12 changes the structure of the amino terminus in connexin- and amino acid- specific ways. This review integrates structural, functional and physiological information about the role of G12 in connexins, focusing on beta-connexins expressed in human epidermis. The importance of G12 substitutions in these beta-connexins is revealed in two hereditary skin disorders, keratitis ichthyosis and erythrokeratodermia variabilis, both of which result from missense mutations affecting G12.
Highlights
glycine at position 12 (G12) Mutation acid 13 is most prevalent [19,20] Cx26Over 300 recessive mutations, mostly point Deafness (GJB2)Skin Disease withDeafness Numerous point mutations, spomutations.dominant35DelG with truncation at amino G12V [21,22,23]Non-syndromic acid 13 is most prevalent [19,20]Keratitis ichthyosis and deaf- radic and hereditary
There a lackproteins of consistency regarding thesignals importance of specific connexins and otheris cellular while responding to cellular that regulate channel behavior. It has become the disruption of G12 causes that and structural elements, likelyapparent relatedthat to intricate differences in changes the structure and are connexin- and circumstance- specific, a logistical complexity that may best be addressed of connexins
This study provided strong evidence that the leak currents and cell death associated with expression of Cx26G12R in oocytes results from aberrant hemichannel behavior
Summary
The human epidermis and is theprevents outermost layer of skin forms a barrier protecting the body from pathogens dehydration [7].that. Gap junctions are important for layers of the epidermis they express a wide of junctional and extracellular proteins both cell adhesion and cell communication in the epidermis, and at least ten connexins that contribute to barrier function and tissue strength [9]. Mutations in Cx43 cause occulodental digital dysplasia Cx26 is expressed th layers of the epidermis along with Cx43 an alpha-type connexin. The only alpha-type connexin so far associated with a hereditary skin disorder is Cx43. Affecting skin, nails and teeth with degenerative components that may involve skin [17,18]
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