Fig. 1.
Cloning of B3SAO and B3EQ into the pBabe neo vector.
Locations of the SAO deletion and the E681Q point mutation are indicated by a gray line in the band 3 cDNAs. For the cloning of B3SAO cDNA into pBabe neo, the 750-bp BstXI-SalI fragment of the previously described construct BSXG1.B3SAO11 was first substituted with the 412-bpBstXI-SalI fragment of pBnB3 (A), thus yielding the construct BSXG1*.B3SAO, which contained a SalI restriction site immediately downstream of the B3SAO cDNA in BSXG1. TheEcoRI-SalI fragment of BSXG1*.B3SAO that included 2066 bp of B3SAO cDNA (encoding the 9 amino acid SAO deletion) was then used to replace the EcoRI-SalI fragment of pBnB3 that included a 2093-bp fragment of B3 cDNA (B), thus generating the construct pBnB3SAO (C). Band 3 cDNA that comprised both the Memphis I polymorphism and the E681Q point mutation was cloned into pBn in 3 steps. The previously described BSXG1.B3 construct29 was used as template for site-directed mutagenesis (Sculptur kit; Amersham, Little Chalfont, United Kingdom), with the oligonucleotide 5′-CATATTCCTGCAGTCTCAGATC-3′ as primer (D). The correct mutant clone (designated BSXG1.B3EQ) was identified by PstI restriction digestion and DNA sequencing. When expressed in Xenopusoocytes, the band 3 protein (B3EQ) encoded by this clone did not mediate chloride transport (data not shown). The 1681-bpEcoRI-BstXI fragment of the B3EQ cDNA that spanned band 3 residues L217 to S773 was excised from the BSXG1.B3EQ construct and subcloned into the BSXG1*.B3SAO construct (E) to give BSXG1*.B3EQ. This construct was subjected toEcoRI-SalI restriction digestion, and the 2093-bp fragment that included the E681Q mutation was cloned into pBnB3 (F), thus generating the desired construct, pBnB3EQ (G). The band 3 coding region was verified in all constructs, using a 377 Applied Biosystems automated DNA sequencer. All vectors were linearized by using theScaI restriction site in pBabe prior to transfections.