The glutamine ligand in the ferrous iron active site of isopenicillin N synthase of Streptomyces jumonjinensis is not essential for catalysis.
Isopenicillin N synthase (IPNS) is a non-heme ferrous iron dependent dioxygenase that catalyses the ring closure of delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine (ACV) to isopenicillin N. We previously used site-directed mutagenesis to identify in the IPNS of Streptomyces jumonjinensis two histidines and one aspartic acid that are essential for activity. The recent crystal structure of the IPNS of Aspergillus nidulans establishes that these amino acids are iron ligands and reveals that the fourth ligand is the penultimate glutamine. The two histidines and one aspartic acid are conserved in several classes of non-heme ferrous iron dioxygenases, whereas the glutamine is present only in IPNSs. In this paper we show that the penultimate glutamine in S. jumonjinensis IPNS Gln-328 is not essential for catalysis. In contrast, Gln-230 which is highly conserved among the above dioxygenases and is proximal to the active site is crucial for activity.
Landman
O
O
Department of Molecular Microbiology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat Aviv, Israel.
Borovok
I
I
Aharonowitz
Y
Y
Cohen
G
G
D001665:Binding Sites; D005296:Ferrous Compounds; D005973:Glutamine / Q000378:metabolism; D007501:Iron; D008024:Ligands; D016296:Mutagenesis; D019159:Nonheme Iron Proteins / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism*; D010105:Oxygenases / Q000378:metabolism*; D013302:Streptomyces / Q000201:enzymology*
D005296:Ferrous Compounds; D008024:Ligands; D019159:Nonheme Iron Proteins; D005973:Glutamine; D007501:Iron; D010088:Oxidoreductases; D010105:Oxygenases; C038370:isopenicillin N synthetase