Membrane interactions of hemoglobin variants, HbA, HbE, HbF and globin subunits of HbA: Effects of aminophospholipids and cholesterol

Abstract

The interaction of hemoglobin with phospholipid bilayer vesicles (liposomes) has been analyzed in several studies to better understand membrane-protein interactions. However, not much is known on hemoglobin interactions with the aminophospholipids, predominantly localized in the inner leaflet of erythrocytes, e.g., phosphatidylserine (PS), phosphatidylethanolamine (PE) in membranes containing phosphatidylcholine (PC). Effects of cholesterol, largely abundant in erythrocytes, have also not been studied in great details in earlier studies. This work therefore describes the study of the interactions of different hemoglobin variants HbA, HbE and HbF and the globin subunits of HbA with the two aminophospholipids in the presence and absence of cholesterol. Absorption measurements indicate preferential oxidative interaction of HbE and alpha-globin subunit with unilamellar vesicles containing PE and PS compared to normal HbA. Cholesterol was found to stabilize such oxidative interactions in membranes containing both the aminophospholipids. HbE and alpha-globin subunits were also found to induce greater leakage of membrane entrapped carboxyfluorescein (CF) using fluorescence measurements. HbE was found to induce fusion of membrane vesicles containing cholesterol and PE when observed under electron microscope. Taken together, these findings might be helpful in understanding the oxidative stress-related mechanism(s) involved in the premature destruction of erythrocytes in peripheral blood, implicated in the hemoglobin disorder, HbE/beta-thalassemia.

RBC electrophoresis with discontinuous power supply – a newly established hemoglobin release test

“…The inner side of the RBC membrane is composed of phosphatidylserine lipids, but these are normally masked by membrane proteins. In cases where abnormal Hbs are increased or when membrane lipids are abnormally exposed, Hbs might interact irreversibly with the lipid layer and distort the membrane 3–6. Apart from the membrane components, Sitdikova 7 demonstrated that the Hb could also interact with serum proteins of mice with Ehrlich carcinoma.…”

Flow Alignment of Extracellular Vesicles: Structure and Orientation of Membrane‐Associated Bio‐macromolecules Studied with Polarized Light

“…The presence of membrane proteins in the samples is also supported by the recorded TEM images (Figure S1). Membrane‐bound hemoglobin molecules were observed earlier for various lipid compositions, as well as for red blood cells . It was even suggested that hemoglobin may dissociate from its tetramer form and that dimer subunits could rather associate with the membranes .…”

Structure‐activity relationship of heme and its analogues in membrane damage and inhibition of fusion

“…The buffer was prepared in triple distilled deionized water from Milli Q source (Millipore Corporation, Massachusetts, USA). 6-CF concentration was measured at 492 nm using molar absorptivity as 72 9 10 3 M À1 Ácm À1 [13].…”