2ohb
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(New page: 200px<br /><applet load="2ohb" size="450" color="white" frame="true" align="right" spinBox="true" caption="2ohb, resolution 1.80Å" /> '''Myoglobin cavity mut...)
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Revision as of 11:03, 21 November 2007
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Myoglobin cavity mutant I107W
Overview
The pathways for ligand entry and exit in myoglobin have now been well, established by a wide variety of experimental results, including pico- to, nano- to microsecond transient absorbance measurements and time-resolved, X-ray crystallographic measurements. Trp insertions have been used to, block, one at a time, the three major cavities occupied by, photodissociated ligands. In this work, we review the effects of the, L29(B10)W mutation, which places a large indole ring in the initial, 'docking site' for photodissociated ligands. Then, the effects of blocking, the Xe4 site with I28W, V68W, and I107W mutations and the Xe1 cavity with, L89W, L104W, and F138W mutations are described. The structures of four of, these mutants are shown for the first time (Trp28, Trp68, Trp107, and Trp, 138 sperm whale metMb). All available results support a 'side path', mechanism in which ligands move into and out of myoglobin by outward, rotation of the HisE7 side chain, but after entry can migrate into, internal cavities, including the distal Xe4 and proximal Xe1 binding, sites. The distal cavities act like the pocket of a baseball glove, catching the ligand and holding it long enough for the histidine gate to, close and facilitate internal coordination with the heme iron atom. The, physiological role of the proximal Xe1 site is less clear because changes, in the size of this cavity have minimal effects on overall O(2) binding, parameters.
About this Structure
2OHB is a Single protein structure of sequence from Physeter catodon with SO4 and HEM as ligands. Full crystallographic information is available from OCA.
Reference
Ligand pathways in myoglobin: A review of trp cavity mutations., Olson JS, Soman J, Phillips GN Jr, IUBMB Life. 2007 Aug;59(8):552-62. PMID:17701550
Page seeded by OCA on Wed Nov 21 13:10:55 2007
