Steady-state fluorescence and circular dichroism of trout hemoglobins I and IV interacting with tributyltin

Abstract

The effect of tributyltin chloride (TBTC) on rainbow trout (Salmo irideus) hemoglo-bin I (HbI) and hemoglobin IV (HbIV) was characterized by the steady-state fluorescence of intrinsic and extrinsic fluorescent probes. The fluorescence emission spectrum (ex 280 nm) is greatly increased in intensity by the presence of the organotin in both proteins. Circular dichroism spectra in the same samples show a small decrease in 222 , a measure correlated with the percentage of the-helical content. Morever, important changes in near-UV, Soret, and visible regions of CD were induced by TBTC. The correlation of data obtained with trout hemoglo-bins (HbI and HbIV) with similar measurements on globins suggests that the presence of heme is necessary for the interaction of the organotin compound with the proteins. Proteins 1999;34:443-452. 1999 Wiley-Liss, Inc.

Correlation between functional and structural changes of reduced and oxidized trout hemoglobins I and IV at different pHs

“…As the comparison between the structural characteristics of HbI and HbIV, at two different pH values, had been never studied, we have performed these studies by CD, whose spectra acquired in near UV and visible regions are particularly sensitive to heme surrounding. In line with a previous work [3], the near‐UV and visible regions of HbI and HbIV (oxygenated forms, pH 7.8) are characterized by quite different spectra, more evident at the α 1 β 2 interface, as suggested by the CD spectra in the region 270–290 nm (Fig. 1).…”

“…L‐Band (260 nm region) and 270–300 nm region. The 270–300 nm region of CD spectra was used to study changes in the Hb quaternary structure at the α 1 β 2 interface [3,17]. Within the near UV region (1250–300 nm) CD bands are due to aromatic amino acids, S‐S bridges and heme groups [11], and are poorly characterized.…”

“…Our previous CD study [3] demonstrated that the heme–globin interaction in oxy‐HbI and oxy‐HbIV are quite different. The aim of the present paper will be to characterize the heme–globin interaction in iron(II)‐ and met‐HbIV and HbI, at different pH values, by CD.…”

Effects of Fish Heme Protein Structure and Lipid Substrate Composition on Hemoglobin-Mediated Lipid Oxidation

“…At pH 7.4, there were minor differences in the 270-300 nm range between both proteins, suggesting no tangible difference in their quaternary subunit interactions. Both trout and tilapia Hb showed a similar drop in ellipticity at pH 6.3 in the 270-300 nm range, which suggests a modified subunit interaction (35). A drop in ellipticity for both Hb at 285 nm as pH was reduced from 7.4 was indicative of a root effect, where a drop in pH leads to deoxygenation and a shift from the R form to the T form (37).…”

Biological chemistry of organotin compounds: Interactions and dealkylation by dithiols

“…Most studies focus on organotin interactions with hemoglobin [15][16][17][18], liver mitochondria [19][20][21][22][23] and ATPases [24] at a macroscopic level. It is only very recently that attention has been focused on the possible molecular mechanisms of organotin toxicity.…”