Protein structure analysis shuffling

Evidence for domain recruitment has been identified in a wide variety of proteins [47], mechanistically ranging from simple N- or C-terminal fusion to multiple internal insertions and possibly circular permutations [48]. A recent analysis of proteins in the protein structure database (PDB) has further indicated that structural rearrangements as a result of domain shuffling have significantly contributed to today s functional diversity [49]. A brief overview of the various modes of domain recruitment and their effects on function, is presented on examples of /lex-barrel structures. 

Structure analysis of several proteases involved in blood coagulation and fibrinolysis reveals a diverse, sometimes repetitive, assembly of discrete protein modules (Fig. 9.4) [56]. While these modules represent independent structural units with individual folding pathways, their concerted action contributes to function and specificity in the final protein product. On the genetic level, these individual modules are encoded in separate exons. Over the course of modular protein evolution, new genes are created by duplication, deletion, and rearrangement of these exons. Mechanistically, the exon shuffling actually takes place in the intervening intron sequences (intronic recombination - for further details see [10]). 

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