The X-ray Crystallographic Structure and Activity Analysis of a Pseudomonas-Specific Subfamily of the HAD Enzyme Superfamily Evidences a Novel Biochemical Function

Journal Article · Tue Jan 01 04:00:00 EST 2008 · Proteins: Structure, Functions, and Bioinformatics

DOI:https://doi.org/10.1002/prot.21583· OSTI ID:960096

Peisach, E; Wang, L; Burroughs, A; Aravind, L; Dunaway-Mariano, D; Allen, K

The haloacid dehalogenase (HAD) superfamily is a large family of proteins dominated by phosphotransferases. Thirty-three sequence families within the HAD superfamily (HADSF) have been identified to assist in function assignment. One such family includes the enzyme phosphoacetaldehyde hydrolase (phosphonatase). Phosphonatase possesses the conserved Rossmanniod core domain and a C1-type cap domain. Other members of this family do not possess a cap domain and because the cap domain of phosphonatase plays an important role in active site desolvation and catalysis, the function of the capless family members must be unique. A representative of the capless subfamily, PSPTO{_}2114, from the plant pathogen Pseudomonas syringae, was targeted for catalytic activity and structure analyses. The X-ray structure of PSPTO{_}2114 reveals a capless homodimer that conserves some but not all of the intersubunit contacts contributed by the core domains of the phosphonatase homodimer. The region of the PSPTO{_}2114 that corresponds to the catalytic scaffold of phosphonatase (and other HAD phosphotransfereases) positions amino acid residues that are ill suited for Mg+2 cofactor binding and mediation of phosphoryl group transfer between donor and acceptor substrates. The absence of phosphotransferase activity in PSPTO{_}2114 was confirmed by kinetic assays. To explore PSPTO{_}2114 function, the conservation of sequence motifs extending outside of the HADSF catalytic scaffold was examined. The stringently conserved residues among PSPTO{_}2114 homologs were mapped onto the PSPTO{_}2114 three-dimensional structure to identify a surface region unique to the family members that do not possess a cap domain. The hypothesis that this region is used in protein-protein recognition is explored to define, for the first time, HADSF proteins which have acquired a function other than that of a catalyst. Proteins 2008.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: Doe - Office Of Science
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 960096
• Report Number(s): BNL--83082-2009-JA
• Journal Information: Proteins: Structure, Functions, and Bioinformatics, Journal Name: Proteins: Structure, Functions, and Bioinformatics Vol. 70
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AMINO ACIDS
CATALYSIS
CRYSTAL STRUCTURE
DIMERS
ENZYMES
HYDROLASES
HYPOTHESIS
KINETICS
PATHOGENS
PHOSPHOTRANSFERASES
PROTEINS
PSEUDOMONAS
RESIDUES
SUBSTRATES
national synchrotron light source