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commercially available (New England Biolabs, Bev-brand factor with platelet glycoprotein Ib will be published in a separate paper. erly, MA).
In summary, we have described a method of rapid (2) Figure 1 illustrates how a desired chimera ''ab'' and efficient recombination of DNA molecules that can be constructed from templates A and B when an allows one to engineer chimeric proteins. The method amino acid pair (Ala-Ser in the present examples) relies on the presence of an amino acid pair, either at coded by the recognition sequence of a restriction enthe junction site or at one, two, or three amino acids zyme (NheI in the present examples) is present at one away from it, that is coded by the recognition sequence of seven different positions within the junction. The of a restriction endonuclease. Fragments from template amino acids and their corresponding nucleotide se-DNAs are amplified individually using PCR. Through quences around the junction of ab are shown. Primers proper design of the complementary oligodeoxyribo-P2 and P3 are designed such that the amplified fragnucleotide primers, the codon sequence(s) of the amino ments a and b are modified with a NheI site at their acid pair is altered to create the restriction site at the 3 and 5 end, respectively. If the identified amino acid 3 end of the fragment encoding the N-terminal of the pair encoded by a restriction site is present right at the chimera and at the 5 end of the fragment encoding the junction (as in example 1), modifications at the 3 end C-terminal segment. Also, depending on the location of of primer P2 and at the 5 end of primer P3 are minithe amino acid pair that is coded by the recognition mal. Primers are designed such that there is an 18sequence of a restriction site, the ends of the amplified nucleotide sequence that perfectly matches with the DNA fragments are modified such that nucleotide secomplementary strand of the template DNA. When the quences preceding or following the restriction site are identified amino acid pair encoded by a restriction site deleted from one end and added to the other. The amis three amino acids away from the junction (as in explified fragments generate the desired chimera when ample 4), fragment a is amplified such that it is shorter ligated after restriction enzyme digestion. The generby six nucleotides and has a NheI site at its 3 end. ated construct, when expressed, maintains amino acid Amplified fragment b has the NheI site at its 5 end sequence within the chimeric molecule. followed by the six nucleotide sequence left out from a and the 18-nucleotide-long complementary sequence of