Crystallins and gene sharing

Titin is expressed in embryonic and adult cardiac and skeletal muscle. Isoforms with different Mr values are expressed differentially during embryonic development. Evidence suggests that there is a single gene in domestic fowl and that the isoforms are generated by alternate splicing (Tan et al., 1993). 

Contractile proteins and those associated with them show a greater abundance of isoforms than other types of protein. It is generally assumed that these isoforms enable different types of muscle and cytoskeletal protein to have different characteristics appropriate to their physiological functions. However, except in a few cases, e.g. MyHC, it is not yet clear what characteristics are endowed by particular isoforms. It is also clear that expression of these isoforms is regulated both on a temporal basis and spatial basis. Several control elements associated with these multigene families have been identified, but the details of the regulation has still to emerge. 

Type protein composition activity Genetic characteristics studied 

Alpha (aA, Up to 50% 20 kDa subunits Small heat shock 3 exons oA expressed Domestic fowl, duck 

at least Up to 70% 20-30 kDa subunits Protein S of Micrococcus PA1/A3 has 6 exons Domestic fowl 

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