1. 
   Isoform
   Isoform: A protein that has the same function as another protein but which is encoded by a different gene and may have small differences in its sequence. For example, transforming factor beta (TGF-B) exists in three versions, or isoforms (TGF-B1, TGF-B2, and TGF-B3), each of which can set off a sign...
   Found op http://www.medterms.com/script/main/art.html?articlekey=38302
   
   
2. 
   isoform
   A protein having the same function and similar (or identical sequence), but the product of a different gene and (usually) tissue-specific. Rather stronger in implication than `homologous'.
   Found op http://www.encyclo.co.uk/visitor-contributions.php
   
   
3. 
   isoform
   <biochemistry> A protein having the same function and similar (or identical sequence), but the product of a different gene and usually) tissue specific. Rather stronger in implication than homologous. ... (15 Oct 1997) ...
   Found op http://www.mondofacto.com/facts/dictionary?isoform
   
   

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