Abstract
Tetrameric hemoglobin from the "fat innkeeper" worm Urechis caupo possesses a novel subunit arrangement having an "inside out" quaternary structure in that the G/H helices are located on the outer surface of the tetramer. A 5-A resolution crystal structure reveals that although the individual subunits are beta-like, having a distinct D helix and the general myoglobin fold, the subunit contacts are very different from those previously observed for hemoglobins. Furthermore, the hemoglobin from U. caupo is also quite different from the unusual hemoglobin tetramer from clam which also has its G/H helices on the outer surface but with the hemes in close proximity through E-F helical contacts (Royer, W. E., Jr., Love, W. E., and Fenderson, F. F. (1985) Nature 316, 277-280).
Highlights
Tetrameric hemoglobin from the “fat innkeeper” worm Urechis caupo possesses a novel subunit arrangementhaving an “insideout”quaternarystructure in that the G/H helices ?re located on the outer surface of the tetramer
The hemoglobin from U. caupo is quite different from the unusual hemoglobin tetramer from clam which has its G/H helices on the outer surface but with the hemes in close proximity through E-F helical contacts
In thispaper we report the three-dimensional structure of U. caupoohemoglobin, as determined by x-ray crystallography at 5.0 A resolution
Summary
Novel Subunit Structure Observedfor Noncooperative Hemoglobin from Urechis caupo* Tetrameric hemoglobin from the “fat innkeeper” worm Urechis caupo possesses a novel subunit arrangementhaving an “insideout”quaternarystructure in that the G/H helices ?re located on the outer surface of the tetramer. A 5-A resolution crystal structure reveals that the individual subunits are 8like, havinga distinct D helix and the general myoglobin fold, the subunit contacts are very different from those previously observed for hemoglobins.
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