2OH8

Myoglobin cavity mutant I28W

Summary for 2OH8

• Entry DOI: 10.2210/pdb2oh8/pdb
• Related: 2OH9 2OHA 2OHB
• Descriptor: Myoglobin, SULFATE ION, PROTOPORPHYRIN IX CONTAINING FE, ... (4 entities in total)
• Functional Keywords: myoglobin, ligand entry and exit pathways, oxygen storage-transport complex, oxygen storage/transport
• Biological source: Physeter catodon (sperm whale)
• Total number of polymer chains: 1
• Total formula weight: 18246.83

Authors

Phillips Jr., G.N.,Soman, J.,Olson, J.S. (deposition date: 2007-01-09, release date: 2007-01-23, Last modification date: 2023-12-27)

Primary citation

Olson, J.S.,Soman, J.,Phillips, G.N.
Ligand pathways in myoglobin: A review of trp cavity mutations.
Iubmb Life, 59:552-562, 2007

PubMed Abstract: 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.

PubMed: 17701550
DOI: 10.1080/15216540701230495

Experimental method

X-RAY DIFFRACTION (1.8 Å)