Molecular complementarity between tetracycline and the GTPase active site of elongation factor Tu

Abstract

Two crystal forms of a complex between trypsin-modified elongation factor Tu-MgGDP from Escherichia coli and the antibiotic tetracycline have been solved by X-ray diffraction analysis to resolutions of 2.8 and 2.1 A, respectively. In the P2(1) form, cocrystals were grown from a solution mixture of the protein and tetracycline. Six copies of the trypsin-modified EF-Tu-MgGDP-tetracycline complex are arranged as three sets of dimers in the asymmetric unit. In the second crystal form, tetracycline was diffused into P4(3)2(1)2 crystals, resulting in a monomeric complex in the asymmetric unit. Atomic coordinates have been refined to crystallographic R factors of 18.0% for the P2(1) form and 20.0% for the P4(3)2(1)2 form. In both complexes, tetracycline makes significant interactions with the GTPase active site of EF-Tu. The phenoldiketone moiety of tetracycline interacts directly with the Mg(2+), the alpha-phosphate group of GDP and two amino acids, Thr25 and Asp80, which are conserved in the GX(4)GKS/T and DX(2)G sequence motifs found in all GTPases and many ATPases. The molecular complementarity, previously unrecognized between invariant groups present in all GTPase/ATPases and the active moiety of tetracycline, may have wide-ranging implications for all drugs containing the phenoldiketone moiety as well as for the design of new compounds targeted against a broad range of GTPases or ATPases.

Nonantibiotic Properties of Tetracyclines: Structural Basis for Inhibition of Secretory Phospholipase A2

“…Divalent metal coordination is a prerequisite for the antibiotic function of tetracyclines. [31][32][33][34] Thus, tetracyclines bind in complex with a divalent metal ion, presumably Mg 2+ , in vivo as [Mg Tc] + to effect their antibiotic function. 33,35 The [Mg Tc] + complex was also identified as the efflux compound in a widespread tetracycline resistance mechanism driven by proton motive force.…”

“…36 This metal binding mode was observed when tetracycline acted as an inducer of Tet repressor, 37,38 as an inhibitor of bacterial protein biosynthesis at the 30S ribosomal subunit, 31,32 and in complex with elongation factor Tu. 34 Also mandatory for antibiotic activity are hydrophilic and charged substituents along positions 1-4 and 10-12 of the tetracycline framework. In contrast to this binding mode, the PLA 2 structure shows a completely different recognition of the antibiotic compound.…”

Tetracycline does not directly inhibit the function of bacterial elongation factor Tu

“…The structure of a 1:1 complex of trypsin-modified EF-Tu•GDP and tetracycline, solved using X-ray crystallography, supports a putative role of tetracycline in interfering with efficient nucleotide exchange in vivo [21]. Tetracycline is bound to the GTPase domain and interacts with several key functional residues within conserved motifs found in the GTPase and ATPase super families (Fig 1A).…”

Spectroscopic characterization of complexes of tetracycline with cobalt(II), nickel(II), cadmium(II) and inorganic Sn(II)

“…Pharmacokinetics and bioavailability of TC is affected by metal coordination. In blood plasma, the drug is transported as calcium complexes [2]. In the intracellular medium, magnesium complexes seem to be more important *Corresponding author.…”