Table 2. Growth Rates Supported by CBS Variants in a hem1Δ Background.

Substituted Residue	400 ng/mL B6 and 50 µg/mL δ-ALA	400 ng/mL B6 and 5 µg/ml δ-ALA	2 ng/mL B6 and 50 µg/ml δ-ALA	2 ng/mL B6 and 5 µg/mL δ-ALA
V118G	0.90 ± 0.06	0.78 ± 0.12	0.60 ± 0.15	0.56 ± 0.07
I142V	0.82 ± 0.07	0.74 ± 0.12	0.69 ± 0.14	0.87 ± 0.08
L181A	0.64 ± 0.06	0.59 ± 0.03	0.57 ± 0.09	0.59 ± 0.08
N225S	0.74 ± 0.11	0.66 ± 0.06	0.55 ± 0.12	0.45 ± 0.07
K267E	0.61 ± 0.00	n/d	0.57 ± 0.18	n/d
I286A	0.64 ± 0.03	0.58 ± 0.02	0.46 ± 0.06	0.34 ± 0.05
L293V	0.69 ± 0.07	0.67 ± 0.10	0.47 ± 0.07	0.36 ± 0.06
L345P	0.58 ± 0.01	0.07 ± 0.03	0.25 ± 0.06	0.05 ± 0.01
F385L	0.77 ± 0.05	0.69 ± 0.07	0.58 ± 0.10	0.54 ± 0.11

Relative growth rates of a subset of 9 B6-remediable single amino-acid human CBS substitutions expressed in yeast are listed. Each variant was grown in four media conditions; 400 ng/mL pyridoxine and 50 µg/mL ∂-ALA, 400 ng/mL pyridoxine and 5 µg/mL ∂-ALA, 2 ng/mL pyridoxine and 50 µg/mL ∂-ALA, and 2 ng/mL pyridoxine and 5 µg/mL ∂-ALA. As in Table 1, growth rates are expressed as a percentage relative to the yeast strain expressing the major allele of human CBS grown with the same media. Averages were determined from at least three independent yeast transformants of each CBS variant. Conditions in which a variant was unable to grow sufficiently to determine a growth rate are indicated (n/d). CBS, cystathionine β-synthase.