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PDBsum entry 3n4t
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Unknown function
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PDB id
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3n4t
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References listed in PDB file
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Key reference
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Title
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Crystal structure and kinetic mechanism of aminoglycoside phosphotransferase-2''-Iva.
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Authors
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M.Toth,
H.Frase,
N.T.Antunes,
C.A.Smith,
S.B.Vakulenko.
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Ref.
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Protein Sci, 2010,
19,
1565-1576.
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PubMed id
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Abstract
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Acquired resistance to aminoglycoside antibiotics primarily results from
deactivation by three families of aminoglycoside-modifying enzymes. Here we
report the kinetic mechanism and structure of the aminoglycoside
phosphotransferase 2"-IVa (APH(2")-IVa), an enzyme responsible for resistance to
aminoglycoside antibiotics in clinical enterococcal and staphylococcal isolates.
The enzyme operates via a Bi Bi sequential mechanism in which the two substrates
(ATP or GTP and an aminoglycoside) bind in a random manner. The APH(2")-IVa
enzyme phosphorylates various 4,6-disubstituted aminoglycoside antibiotics with
catalytic efficiencies (k(cat)/K(m)) of 1.5 x 10(3) to 1.2 x 10(6) (M(-1)
s(-1)). The enzyme uses both ATP and GTP as the phosphate source, an extremely
rare occurrence in the phosphotransferase and protein kinase enzymes. Based upon
an analysis of the APH(2")-IVa structure, two overlapping binding templates
specifically tuned for hydrogen bonding to either ATP or GTP have been
identified and described. A detailed understanding of the structure and
mechanism of the GTP-utilizing phosphotransferases is crucial for the
development of either novel aminoglycosides or, more importantly, GTP-based
enzyme inhibitors which would not be expected to interfere with crucial
ATP-dependent enzymes.
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