Exon shuffling

The following papers, from 1994, present an interesting, if not well documented, method which uses a radically different selection protocol. Reviewing the literature, however, I am not aware of it having been used effectively by any other laboratory. It should, perhaps, therefore, be considered under the heading of emerging technologies . 

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Segmental dupfications have been found to be much mote common than in the toundwotm or fruit fly. It is possible that these stmctutes may be involved in exon shuffling and the incteased divetsity of proteins found in humans. 

Kolkman, J.A. and Stemmer, W.P. (2001) Directed evolution of proteins by exon shuffling. Nature Biotechnology, 19, 423-428. 

This domain structure, which is remarkably conserved for every assimilatory NR coding sequence, is a good example of evolution by gene fusion. It is often claimed that this results from exon shuffling, each exon coding for a functional unit (Campbell Kinghorn, 1990 Dorit et al.,... 

Exon shuffling no homology required high percentage of functional clones limited to intron-containing genes diversity is proportional to the number of exons Kolkman, 2001... 

B. Differential Splicing of Titin Exon Shuffling Creates Functionally... 

Maki R, Traunecker A, Sakano H, Roeder W, Tonegawa S (1980), Exon shuffling generates an immunoglobulin heavy chain gene, Proc. Natl Acad. Sci. USA 77 2138-2142. 

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]). 

The significance of exon shuffling to protein evolution, in particular in respect to the development of multicellularity, is signified by a short inventory of processes involving proteins created by modular assembly. Exon shuffling facilitates the construction of proteins involved in regulation of blood coagulation, fibrinolysis, and complement activation, plus most constituents of the extracellular matrix, cell adhesion proteins, and receptor proteins [10, 57]. 

Advances in molecular biology and high-throughput screening, as well as the projected flexibility and diversity of modular assembly in natural protein evolution has inspired the development of various techniques to implement combinatorial domain recombination, better known as exon shuffling, in vitro. 

Fig. 9.9. Exon shuffling combinatorial libraries of multidomain enzymes can be created through recombination of individual modules or domains (I - IV) from multiple parents (A - D) in an ordered fashion, maintaining the parental size (left diagram) or by random reassembly. This allows...

Figure 5.36. Exon Shuffling. Exons can be readily shuffled by recombination of DNA to expand the genetic repertoire.

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