Palmitate interaction with physiological states of myoglobin

Abstract

Background Previous studies have shown that palmitate (PA) can bind specifically and non-specifically to Fe (III) MbCN. The present study has observed PA interaction with physiological states of Fe (II) Mb, and the observations support the hypothesis that Mb may have a potential role in facilitating intracellular fatty acid transport. Methods 1H NMR spectra measurements of the Mb signal during PA titration show signal changes consistent with specific and non-specific binding. Results Palmitate (PA) interacts differently with physiological states of Mb. Deoxy Mb does not interact specifically or non-specifically with PA, while the carbonmonoxy myoglobin (MbCO) interaction with PA decreases the intensity of selective signals and produces a 0.15 ppm upfield shift of the PA methylene peak. The selective signal change upon PA titration provides a basis to determine an apparent PA binding constant, which serves to create a model comparing the competitive PA binding and facilitated fatty acid transport of Mb and fatty acid binding protein (FABP). Conclusions Given contrasting PA interaction of ligated vs. unligated Mb, the cellular fatty acid binding protein (FABP) and Mb concentration in the cell, the reported cellular diffusion coefficients, the PA dissociation constants from ligated Mb and FABP, a fatty acid flux model suggests that Mb can compete with FABP transporting cellular fatty acid. General Significance Under oxygenated conditions and continuous energy demand, Mb, dependent fatty acid transport could influence the cell’s preference for carbohydrate or fatty acid as a fuel source and regulate fatty acid metabolism.

Novel Molecular Interactions of Acylcarnitines and Fatty Acids with Myoglobin

“…Docking results for these ligands with deoxy-Mb showed no favorable binding, consistent with previous MD studies and experimental results with LCFAs (23,27) (Fig. 1, A and C).…”

Interaction of myoglobin with oleic acid

“…Given the selective change of the 8 heme methyl signal and an apparent signal intensity plateau at about OA:Mb 2:1, which the data analysis has presumed to correspond to a fully OA bound Mb (Mb-OA) state, a graph of the fractional amount of Mb-OA as a function of OA leads to the determination of an apparent K d = 45 μM for the specific OA binding to MbCN, fig 2 (47; 48). …”

“…The results suggest that Mb could serve as a fatty acid transporter and use a convenient loading-unloading mechanism that follows the O 2 gradient from the sarcolemma to the mitochondria. In fact, a fatty acid transport model indicates that Mb can compete effectively with fatty acid binding protein (FABP) above a fatty acid concentration threshold (47). …”

“…Moreover, the Mb interaction with OA does not appear to arise from any alteration in the lamella-micelle equilibrium. Given the specific interaction of OA, a model of intracellular fatty acid transport indicates that Mb can compete with fatty acid binding protein (FABP) to transport both saturated and unsaturated fatty acid in the cell (16; 33; 34; 47; 48). Mb may then have a role in regulating fatty acid metabolism and presents a unique model to interrogate protein-fatty acid interaction.…”

High fatty acid oxidation capacity and phosphorylation control despite elevated leak and reduced respiratory capacity in northern elephant seal muscle mitochondria

“…Therefore, NES mitochondria likely maintain comparatively high lipid OXPHOS capacity by a selective increase in the transport, oxidation and/or delivery of reducing equivalents derived from fatty acids to the respiratory system. Notably, myoglobin has been reported to facilitate myocellular transport of fatty acids under oxygenated conditions (Shih et al, 2014) and is far more abundant in NES versus human muscle in vivo (Gros et al, 2010;Hassrick et al, 2010). The vast majority of myoglobin is leached from fibers during the preparation and permeabilization procedure to avoid confounding effects on O 2 transport.…”