title: Association of a Zn(2+) containing metallo β-lactamase with the anticancer antibiotic mithramycin.
abstract: Pathogenic bacteria that are resistant to β-lactam antibiotics mostly utilize serine β-lactamases to degrade the antibiotics. Current studies have shown that different subclasses of metallo β-lactamases (E[MBL]) are involved in the defense mechanism of drug resistant bacteria. Here we report that the Zn(2+) containing subclass B1 E[MBL] from Bacillus cereus binds to a naturally occurring anti-cancer drug mithramycin (MTR). Spectroscopic (CD and fluorescence) and isothermal titration calorimetry studies show that MTR forms a high affinity complex with the Zn(2+) ion containing E[MBL]. Abolished interaction of MTR with apo E[MBL] suggests that the formation of this high affinity complex occurs due to the potential of MTR to bind bivalent metal ions like Zn(2+). Furthermore, CD spectroscopy, dynamic light scattering and differential scanning calorimetry studies indicate that the strong association with sub-micromolar dissociation constant leads to an alteration in the enzyme conformation at both secondary and tertiary structural levels. The enzyme activity decreases as a consequence to this conformational disruption arising from the formation of a ternary complex involving MTR, catalytic Zn(2+) and the enzyme. Our results suggest that the naturally occurring antibiotic MTR, a generic drug, has the potential as an E[MBL] inhibitor.
authors.affiliation: Biophysics Division, Saha Institute of Nuclear Physics, 1/AF Sector-1, Bidhannagar, Kolkata 700064, India. Electronic address: Shibojyoti.Lahiri@med.uni-muenchen.de.
authors.forename: Shibojyoti
authors.initials: S
authors.lastname: Lahiri
authors.affiliation: Biophysics Division, Saha Institute of Nuclear Physics, 1/AF Sector-1, Bidhannagar, Kolkata 700064, India.
authors.forename: Amrita
authors.initials: A
authors.lastname: Panja
authors.affiliation: Biophysics Division, Saha Institute of Nuclear Physics, 1/AF Sector-1, Bidhannagar, Kolkata 700064, India. Electronic address: dipak.dasgupta@saha.ac.in.
authors.forename: Dipak
authors.initials: D
authors.lastname: Dasgupta
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000737:chemistry*; D001409:Bacillus cereus / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry*; D008926:Plicamycin / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*; D001618:beta-Lactamases / Q000737:chemistry*
chemical_list: D000903:Antibiotics, Antineoplastic; D001426:Bacterial Proteins; D001618:beta-Lactamases; D015032:Zinc; D008926:Plicamycin
keywords: Enzyme inhibition; Metal ion binding; Metallo β-lactamase; Metalloenzyme; Mithramycin