TY - JOUR
T1 - Cloning, sequencing, and expression of the Pseudomonas putida protocatechuate 3,4-dioxygenase genes
AU - Frazee, R. W.
AU - Livingston, D. M.
AU - LaPorte, D. C.
AU - Lipscomb, J. D.
PY - 1993
Y1 - 1993
N2 - The genes that encode the α and β subunits of protocatechuate 3,4- dioxygenase (3,4-PCD [EC 1.13.11.3]) were cloned from a Pseudomonas putida (formerly P. aeruginosa) (ATCC 23975) genomic library prepared in λ phage. Plaques were screened by hybridization with degenerate oligonucleotides designed using known amino acid sequences. A 1.5-kb SmaI fragment from a 15- kb primary clone was subcloned, sequenced, and shown to contain two successive open reading frames, designated pcaH and pcaG, corresponding to the β and α subunits, respectively, of 3,4-PCD. The amino acid sequences deduced from pcaHG matched the chemically determined sequence of 3,4-PCD in all except three positions. Cloning of pcaHG into broad-host-range expression vector pKMY319 allowed high levels of expression in P. putida strains, as well as in Proteus mirabilis after specific induction of the plasmid-encoded nahG promoter with salicylate. The recombinant enzyme was purified and crystallized from P. mirabilis, which lacks an endogenous 3,4-PCD. The physical, spectroscopic, and kinetic properties of the recombinant enzyme were indistinguishable from those of the wild-type enzyme. Moreover, the same transient enzyme intermediates were formed during the catalytic cycle. These studies establish the methodology which will allow mechanistic investigations to be pursued through site-directed mutagenesis of P. putida 3,4-PCD, the only aromatic ring-cleaving dioxygenase for which the three-dimensional structure is known.
AB - The genes that encode the α and β subunits of protocatechuate 3,4- dioxygenase (3,4-PCD [EC 1.13.11.3]) were cloned from a Pseudomonas putida (formerly P. aeruginosa) (ATCC 23975) genomic library prepared in λ phage. Plaques were screened by hybridization with degenerate oligonucleotides designed using known amino acid sequences. A 1.5-kb SmaI fragment from a 15- kb primary clone was subcloned, sequenced, and shown to contain two successive open reading frames, designated pcaH and pcaG, corresponding to the β and α subunits, respectively, of 3,4-PCD. The amino acid sequences deduced from pcaHG matched the chemically determined sequence of 3,4-PCD in all except three positions. Cloning of pcaHG into broad-host-range expression vector pKMY319 allowed high levels of expression in P. putida strains, as well as in Proteus mirabilis after specific induction of the plasmid-encoded nahG promoter with salicylate. The recombinant enzyme was purified and crystallized from P. mirabilis, which lacks an endogenous 3,4-PCD. The physical, spectroscopic, and kinetic properties of the recombinant enzyme were indistinguishable from those of the wild-type enzyme. Moreover, the same transient enzyme intermediates were formed during the catalytic cycle. These studies establish the methodology which will allow mechanistic investigations to be pursued through site-directed mutagenesis of P. putida 3,4-PCD, the only aromatic ring-cleaving dioxygenase for which the three-dimensional structure is known.
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U2 - 10.1128/jb.175.19.6194-6202.1993
DO - 10.1128/jb.175.19.6194-6202.1993
M3 - Article
C2 - 8407791
AN - SCOPUS:0027508335
SN - 0021-9193
VL - 175
SP - 6194
EP - 6202
JO - Journal of bacteriology
JF - Journal of bacteriology
IS - 19
ER -