ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
O1. Molecular Probes for the Active Site of P450cam and iNOS
D.B. Goodin a , R.F. Wilson a , P. Glazer a , A. Annalora a , C.D. Stout a , and H.B. Gray b
a Dept. of Molecular Biology, The Scripps Research Institute, 10550 N. Torrey Pines Rd, La Jolla, CA
b Dept. of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA
Several families of molecular wires have been developed to probe the active site channels of P450cam and
murine iNOS heme domain. These wires consist of ligand analogs tethered to a reporter, sensitizer or molecular
surface. This allows photochemically or electrochemically initiated redox reactions to be explored, and offers a
method for affinity based selection of binding behavior. We have examined the structural response of a series
P450cam specific probes that vary in the position of hydrogen bonding groups, linker length and composition.
Crystallographic structures reveal a significant structural plasticity of the distal substrate binding channel that
arise from combinations of several modes of movements in the F, G, and B' helices. Changes in the hydrogen
bonding interactions between wire and protein were observed to affect ligand orientation more than binding
affinity, while the linker length and hydrophobicity have a significant impact on the conformation disorder in
both the wire and protein. A separate family of wires using analogs of 6(R)-tetrahydro-L-biopterin (H4B) linked
to Ru based photosensitizers were shown to bind to pterin free iNOS heme domain. Photoinduced reduction of
ferric NOS was observed by excitation of the Ru(II) center in the presence of reductive quenchers. These wires
are being examined for their potential to generate unstable intermediates in the NOS reaction cycle.
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