All mutations were generated using the QuikChange (Stratagene) system according to the manufacturer's instructions. The forward primers used to generate amino acid substitutions in pNE9-B2 or pDriT2 are as follows (the substituted bases are underlined): p270.P1042A: GCATGACAAATCTGGCTGCTGTGGGTAGGAAACCp270.W1073A: GGTCAACAAGAACAAAAAAGCGCGGGAACTTGCAACCp270.Y1096A: CCTTGAAAAAGCAGGCTATCCAGTGCTCTATGCDri.P306A: CCGATCAATCGGCTGGCGATAATGGCCAAATCGGDri.W337A: CAACAAGAAGCTGGCGCAGGAGATCATCAAGGGGCDri.Y361A: CCCTGCGCACCCAAGCCATGAAGTATCTGTACCCG The remaining mutations were generated in p410 or pNDB8. The forward primers used to generate amino acids substitutions are as follows (the substituted bases are underlined): Dri.SSS: GCCCTCCAGCATCTCCAGTGCCGCCTCCTCCCTGCGCACCCp270.TFT: GTGGGCACATCAACCAGTGCTGCCTTCACCTTGAAAAAGCAG
