Resonance Raman evidence for an unusually strong exogenous ligand—metal bond in a monomeric nitrosyl manganese hemoglobin

• Published in: FEBS letters 1988-03, Vol.229 (2), p.367-371
• Main Authors: Lin, Shun-Hua, Yu, Nai-Teng, Gersonde, Klaus
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Chironomidae; Chironomus thummi thummi; Fundamental and applied biological sciences. Psychology; Hemoglobin; Hemoglobins - metabolism; Ligands; Manganese; Metal-ligand vibrational mode; Molecular biophysics; Nitric Oxide; nitrosyl manganese; Nitrosyl manganese hemoglobin; Organometallic Compounds - metabolism; Protein Binding; Raman spectroscopy; Resonance Raman spectroscopy; Spectroscopy : techniques and spectras; Spectrum Analysis, Raman - methods
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(88)81158-X

Resonance Raman spectroscopy has been employed to determine the vibrational modes of monomeric nitrosyl manganese Chironomus thummi thummi hemoglobin (CTT IV). This insect hemoglobin has no distal histidine. By applying various isotope-labeled nitric oxides ( 14N 16O, 15N 16O, 14N 18O), we have identified the Mn II-NO stretching mode at 628 cm −1, the Mn II-N-O bending mode at 574 cm −1 and the N-O stretching mode at 1735 cm −1. The results suggest a strong Mn IINO bond and a weak NO bond. The vinyl group substitution does not influence the ν(Mn II-NO), δ(Mn II-N-O) and ν(NO) vibrations. The Mn II-NO stretching frequency is insensitive to distal histidine interactions with NO, whereas the NO stretching frequency is sensitive. Nitric oxide also binds to Met manganese CTT IV to form an Mn III·NO complex which undergoes a slow but complete autoreduction resulting in the Mn II·NO species. In manganese meso-IX CTT IV, the Mn III·NO Mn II·NO conversion alters the intensities of the porphyrin ring modes at 342, 360, 1587 and 1598 cm −1, but shifts the frequencies at 1504 and 1633 cm −1 (in Mn III·NO) to 1497 and 1630 cm −1 (in Mn II·NO), respectively. The unshifted marker line at 1378 cm −1 reflects the fact that the π* electron densities of the porphyrin ring are the same in the two complexes.