The N TAILD1 gene construct, encoding residues 421-525 of the MV N protein with an N-terminal hexahistidine tag plus a C-terminal Flag sequence, was obtained using the plasmid pet21a/N as template. Forward primer (5 0 -gatagaaccatgCA TCATCATCATCATCATcacggtgatcaaagtgagaatgag-3 0 ) was designed to introduce a hexahistidine tag encoding sequence (upper case) at the N terminus of N TAIL , and reverse primer (5 0 -gtcttaTTTGTCGTCATCGTCTTTATAATCgtctagaagattt ctgtcattgta-3 0 ) was designed to introduce a Flag-encoding sequence (upper case). The PCR amplification product was further used as template in a second PCR step, using the same pair of primers as in the second PCR step, which yielded both N TAILD3 and N TAILD2,3 amplification products. After purification, the PCR product was cloned into the pDest14 vector to yield pDest14/N TAILD1 .