Figure 2.

Biochemical analyses of the β-diox encoded by the ninaB^P315 and ninaB^360d alleles compared with the wt allele. (A) The picture shows the color shift of the β-carotene-producing and -accumulating E. coli strain from yellow to white caused by the formation of retinoids from β-carotene by the β-diox enzymatic activity. Although the E. coli strain expressing the β-diox encoded by the wt allele becomes white, the E. coli expressing β-diox encoded by the ninaB^P315 and ninaB^360d alleles remain yellow. A control E. coli strain transformed with the expression vector (pBAD-TOPO) alone remains yellow. (B) HPLC analyses of the products formed in the different E. coli strains. In the E. coli strain expressing β-diox encoded by the wt allele, significant amounts of retinoids are found (upper trace), whereas in the E. coli strain expressing β-diox encoded by the ninaB^P315 (middle trace) or ninaB^360d (lower trace) alleles, no retinoids become detectable.