The emerging periplasm-localized subclass of AroQ chorismate mutases, exemplified by those from Salmonella typhimurium and Pseudomonas aeruginosa.
BACKGROUND
Chorismate mutases of the AroQ homology class are widespread in the Bacteria and the Archaea. Many of these exist as domains that are fused with other aromatic-pathway catalytic domains. Among the monofunctional AroQ proteins, that from Erwinia herbicola was previously shown to have a cleavable signal peptide and located in the periplasmic compartment. Whether or not this might be unique to E. herbicola was unknown.


RESULTS
The gene coding for the AroQ protein was cloned from Salmonella typhimurium, and the AroQ protein purified from both S. typhimurium and Pseudomonas aeruginosa was shown to have a periplasmic location. The periplasmic chorismate mutases (denoted *AroQ) are shown to be a distinct subclass of AroQ, being about twice the size of cytoplasmic AroQ proteins. The increased size is due to a carboxy-terminal extension of unknown function. In addition, a so-far novel aromatic aminotransferase was shown to be present in the periplasm of P. aeruginosa.


CONCLUSIONS
Our analysis has detected a number of additional *aroQ genes. The joint presence of *AroQ, cyclohexadienyl dehydratase and aromatic aminotransferase in the periplasmic compartment of P. aeruginosa comprises a complete chorismate-to-phenylalanine pathway and accounts for the "hidden overflow pathway" to phenylalanine described previously.
Calhoun
D H
DH
Department of Chemistry, City College of New York, New York, NY 10031, USA.
Bonner
C A
CA
Gu
W
W
Xie
G
G
Jensen
R A
RA
D000595:Amino Acid Sequence; D002826:Chorismate Mutase / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002827:Chorismic Acid / Q000378:metabolism; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000201:enzymology; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D005810:Multigene Family / Q000235:genetics; D019897:Periplasm / Q000201:enzymology* / Q000378:metabolism; D010649:Phenylalanine / Q000096:biosynthesis / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D012486:Salmonella typhimurium / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013379:Substrate Specificity; D000637:Transaminases / Q000302:isolation & purification / Q000378:metabolism; D014443:Tyrosine / Q000096:biosynthesis
D011994:Recombinant Proteins; D014443:Tyrosine; D010649:Phenylalanine; D000637:Transaminases; D002826:Chorismate Mutase; D002827:Chorismic Acid