1IOP

INCORPORATION OF A HEMIN WITH THE SHORTEST ACID SIDE-CHAINS INTO MYOGLOBIN

Summary for 1IOP

• Entry DOI: 10.2210/pdb1iop/pdb
• Descriptor: MYOGLOBIN, CYANIDE ION, SULFATE ION, ... (5 entities in total)
• Functional Keywords: oxygen transport, globin fold
• Biological source: Physeter catodon (sperm whale)
• Total number of polymer chains: 1
• Total formula weight: 17893.39

Authors

Igarashi, N.,Neya, S.,Funasaki, N.,Tanaka, N. (deposition date: 1997-12-12, release date: 1998-04-08, Last modification date: 2024-04-03)

Primary citation

Neya, S.,Funasaki, N.,Igarashi, N.,Ikezaki, A.,Sato, T.,Imai, K.,Tanaka, N.
Structure and function of 6,7-dicarboxyheme-substituted myoglobin
Biochemistry, 37:5487-5493, 1998

PubMed Abstract: Myoglobin was reconstituted with 6,7-dicarboxy-1,2,3,4,5, 8-hexamethylheme, a compact synthetic heme with the shortest acid side chains, to pursue the structural and functional consequences after intensive disruption of the heme propionate-apoglobin linkages in the native protein. The electron-withdrawing carboxylate groups directly attached to the porphyrin ring lowered the oxygen affinity by 3-fold as compared with native myoglobin. Autoxidation of the oxy derivative to the ferric protein proceeded with 1.6 x 10(-)2 min-1 at pH 7.0 and 30 degrees C. The crystallographic structure of the cyanomet myoglobin with 1.9 A resolution shows that the heme adopts a unique orientation in the protein pocket to extend the two carboxylates toward solvent sphere. The native globin fold is conserved, and the conformations of globin side chains are almost intact except for those located nearby the heme 6,7-carboxylates. The 7-carboxylate only weakly interacts with Ser92 and His97 through two mediating water molecules. The 6-carboxylate, on the other hand, forms a novel salt bridge with Arg45 owing to conformational flexibility of the guanidinium side chain. The proton NMR shows that the small heme does not fluctuate about the iron-histidine bond even at 55 degreesC, suggesting that the salt bridge between Arg45 and heme 6-carboxylate is of critical importance to recognize and fix the heme in myoglobin.

PubMed: 9548931
DOI: 10.1021/bi972632c

Experimental method

X-RAY DIFFRACTION (1.9 Å)