TY - JOUR
T1 - Structural and functional characterization of the paai thioesterase from Streptococcus pneumoniae reveals a dual specificity for phenylacetyl-CoA and medium-chain fatty Acyl-CoAs and a novel CoA-induced fit mechanism
AU - Khandokar, Yogesh B.
AU - Srivastava, Parul
AU - Sarker, Subir
AU - Swarbrick, Crystall M.D.
AU - Aragao, David
AU - Cowieson, Nathan
AU - Forwood, Jade K
PY - 2016/1/22
Y1 - 2016/1/22
N2 - PaaI thioesterases are members of the TE13 thioesterase family that catalyze the hydrolysis of thioester bonds between coenzyme A and phenylacetyl-CoA. In this study we characterize the PaaI thioesterase from Streptococcus pneumoniae (SpPaaI), including structural analysis based on crystal diffraction data to 1.8-Å resolution, to reveal two double hotdog domains arranged in a back to back configuration. Consistent with the crystallography data, both size exclusion chromatography and small angle x-ray scattering data support a tetrameric arrangement of thioesterase domains in solution. Assessment of SpPaaI activity against a range of acyl-CoA substrates showed activity for both phenylacetyl-CoA and medium-chain fatty-acyl CoA substrates. Mutagenesis of putative active site residues reveals Asn37, Asp52, and Thr68 are important for catalysis, and size exclusion chromatography analysis and x-ray crystallography confirm that these mutants retain the same tertiary and quaternary structures, establishing that the reduced activity is not a result of structural perturbations. Interestingly, the structure of SpPaaI in the presence of CoA provides a structural basis for the observed substrate specificity, accommodating a 10-carbon fatty acid chain, and a large conformational change of up to 38 Å in the Nterminus, and a loop region involving Tyr38-Tyr39. This is the first time PaaI thioesterases have displayed a dual specificity for medium-chain acyl-CoAs substrates and phenylacetyl-CoA substrates, and we provide a structural basis for this specificity, highlighting a novel induced fit mechanism that is likely to be conserved within members of this enzyme family.
AB - PaaI thioesterases are members of the TE13 thioesterase family that catalyze the hydrolysis of thioester bonds between coenzyme A and phenylacetyl-CoA. In this study we characterize the PaaI thioesterase from Streptococcus pneumoniae (SpPaaI), including structural analysis based on crystal diffraction data to 1.8-Å resolution, to reveal two double hotdog domains arranged in a back to back configuration. Consistent with the crystallography data, both size exclusion chromatography and small angle x-ray scattering data support a tetrameric arrangement of thioesterase domains in solution. Assessment of SpPaaI activity against a range of acyl-CoA substrates showed activity for both phenylacetyl-CoA and medium-chain fatty-acyl CoA substrates. Mutagenesis of putative active site residues reveals Asn37, Asp52, and Thr68 are important for catalysis, and size exclusion chromatography analysis and x-ray crystallography confirm that these mutants retain the same tertiary and quaternary structures, establishing that the reduced activity is not a result of structural perturbations. Interestingly, the structure of SpPaaI in the presence of CoA provides a structural basis for the observed substrate specificity, accommodating a 10-carbon fatty acid chain, and a large conformational change of up to 38 Å in the Nterminus, and a loop region involving Tyr38-Tyr39. This is the first time PaaI thioesterases have displayed a dual specificity for medium-chain acyl-CoAs substrates and phenylacetyl-CoA substrates, and we provide a structural basis for this specificity, highlighting a novel induced fit mechanism that is likely to be conserved within members of this enzyme family.
UR - http://www.scopus.com/inward/record.url?scp=84959020456&partnerID=8YFLogxK
U2 - 10.1074/jbc.M115.677484
DO - 10.1074/jbc.M115.677484
M3 - Article
AN - SCOPUS:84959020456
VL - 291
SP - 1866
EP - 1876
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 1083-351X
IS - 4
ER -