**Function**

Gap junctions were first characterized by electron microscopy as regionally specialized structures on plasma membranes of contacting adherent cells. These structures were shown to consist of cell-to-cell channels. Proteins, called connexins, purified from fractions of enriched gap junctions from different tissues differ. The connexins are designated by their molecular mass. Another system of nomenclature divides gap junction proteins into 2 categories, alpha and beta, according to sequence similarities at the nucleotide and amino acid levels. For example, CX43 (MIM 121014) is designated alpha-1 gap junction protein, whereas CX32 (GJB1; MIM 304040) and CX26 (this protein) are called beta-1 and beta-2 gap junction proteins, respectively. This nomenclature emphasizes that CX32 and CX26 are more homologous to each other than either of them is to CX43.

Read more about this topic: GJB2

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### Famous quotes containing the word function:

“The press and politicians. A delicate relationship. Too close, and danger ensues. Too far apart and democracy itself cannot *function* without the essential exchange of information. Creative leaks, a discreet lunch, interchange in the Lobby, the art of the unattributable telephone call, late at night.”

—Howard Brenton (b. 1942)

“The *function* of muscle is to pull and not to push, except in the case of the genitals and the tongue.”

—Leonardo Da Vinci (1425–1519)

“The more books we read, the clearer it becomes that the true *function* of a writer is to produce a masterpiece and that no other task is of any consequence.”

—Cyril Connolly (1903–1974)