Abstract
The crystal structure of Asian elephant cyano-metmyoglobin which has a glutamine instead of the usual distal site histidine has been determined to high resolution. In addition to this replacement, the substitution of a conserved leucine residue in position 29(B10) at the distal side by a phenylalanine was unambiguously identified based on the available electron density. The suspicion, that there were errors in the original sequence which has caused some confusion, is thus confirmed. Comparison with other myoglobin structures in various ligated forms reveals an essentially unchanged tertiary structure in elephant myoglobin despite the two amino acid substitutions in the heme pocket. Our current structural model shows that the N epsilon 2 atom of Gln64(E7) has moved with respect to the corresponding nitrogen position of His64(E7) in the CO complex of sperm whale myoglobin. The newly assigned residue Phe29(B10) penetrates into the distal side of the heme pocket approaching the ligand within van der Waals distance and causing a much more crowded heme pocket compared to other myoglobins. Kinetic properties of Asian elephant myoglobin, wild type, and recombinant sperm whale myoglobins are discussed in relation to the structural consequences of the two amino acid substitutions H64Q and L29F.
Highlights
From the Laboratory of Biochemistry I, Swiss Federal Institute of Technology, CH-B092 Zurich, Switzerland and the slnstitut fur Biophysih, Unioersitiit Freiburg, D-79104 Freiburg, Germany
Kinetic properties of Asian elephant myoglobin, wild type, and recombinant sperm whale myoglobins are discussed in relation to the structural consequences of the two amino acid substitutions H64Q and L29F
The results presented here show that the primary structure reported by Dene et al, [8] contains a crucial error and a phenylalanine is present at position 29 (BID) of EMb
Summary
Vol 270, No 35, Issue of September 1, pp. 20754-20762, 1995 Printed in U.S.A. Daniel A. A 5-fold decrease of the O2 binding constant and a 3-fold increase in the rate of autooxidation were observed This single amino acid change in the distal side, deduced from the reported primary sequence, is not sufficient to explain the kinetic properties of Asian elephant myoglobin which are similar to myoglobins having the usual histidine E7. Yu et al, [12] and Vyas et al, [13] have reported proton NMR spectra of Asian elephant myoglobin These data were interpreted in terms of the presence of an additional phenylalanine in the heme crevice close enough to the prosthetic group to interact with the bound ligand. Phe29(BlO) is in close contact with the bound ligand and occupies the cavity in which the free CO is found in the 40 K crystal structure of photolyzed SWMb recently reported by Schlichting et al, [16]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
