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Fig. 4 | BMC Plant Biology

Fig. 4

From: Determinants of substrate specificity in a catalytically diverse family of acyl-ACP thioesterases from plants

Fig. 4

Structural composition, substrate specificity, and productivity of wild-type and mutant ALTs in E. coli. The structural composition of chimeric ALT proteins is represented by coloured blocks. Sequence fragments exchanged between ALT pairs to create chimeric enzyme variants are annotated as follows: A = aa31–36, B = aa108–111, C = aa78–93, D = aa94–96, E = aa64–67. Residue positions are numbered beginning from the N-terminus of the hot-dog fold thioesterase domain; a predicted N-terminal plastid targeting sequence has been excluded [20, 24]. Production of individual fatty acid and methylketone species (in mol% of total products), on average, by wild-type and chimeric ALTs in E. coli is summarized in three tables, with darker cell shading representing greater proportions (scale shown above tables). Lowercase letters approximate sample means. Mean values in each column sharing a common letter did not differ significantly according to the appropriate statistical test (Tukey’s HSD test or Dunn’s test at the α = 0.01 significance level). Spaces that do not contain letters represent mean values that did not differ statistically from zero, or from an E. coli strain harbouring an empty pET28a vector according to a right-tailed Student’s t-test (p < 0.05, p-values adjusted using the Holm-Šidak correction). β-keto fatty acids produced by ALTs were decarboxylated to methylketones prior to identification and quantification by GC-MS and GC-FID analysis. The total productivity of ALTs, in units of nmol / mL OD600, is represented by green bars. All quantities reported are the average of triplicate samples (n = 3), and error reported on these values represents ± SE. ALT variants that did not display detectable thioesterase activity in K27(DE3) E. coli were omitted from this figure

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