A protein isoform is a version of a
proteinwith only small differences to another isoform of the same protein. [http://en.wiktionary.org/wiki/isoform] Different forms of a protein may be produced from different but related genes, or may arise from the same gene by alternative splicing. A large number of isoforms are caused by single nucleotide polymorphisms, small genetic differences between allelesof the same gene.
The discovery of isoforms explains the apparently small number of coding
genesrevealed in the human genome project: the ability to create categorically different proteins from the same gene increases the diversity of the proteome. Isoforms are readily described and discovered by microarraystudies and cDNAlibraries.
A glycoform is an isoform where different forms of a
glycoproteinhave different polysaccharides attached to them, by either posttranslationalor cotranslationalmodifications.
Creatine kinase, the presence of which in the blood can be used as an aid in the diagnosis of myocardial infarction, exists in 3 isoforms.
Hyaluronan synthase, the enzyme responsible for the production of hyaluronan, has three isoforms in mammalian cells.
* [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=mesh&list_uids=68020033&dopt=Full MeSH entry protein isoforms]
* [http://ghr.nlm.nih.gov/glossary=isoforms Definitions Isoform]
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