Purification and Characterization of a Novel 88 kDa Protein from Serum and Vitreous of Patients with Eales’ Disease

Abstract

Eales’ disease is a perivasculitis that affects the peripheral retina of young adults and results in recurrent vitreous hemorrhage. Although increased oxidative stress and decreased antioxidant defense have been reported to be associated with Eales’ disease, the exact cause for the disease and its pathogenesis are not known. Here is reported the identification, purification and characterization of a new protein from the serum and vitreous of patients with Eales’ disease. This protein was purified using preparative electrophoresis and HPLC. The purified protein had a retention time of 9.2min in RP HPLC. Its molecular weight as determined by gel permeation chromatography was 88kDa hence, it was termed as 88kDa protein. Alcian blue and Schiffs staining revealed 88kDa protein to be a glycoprotein. Proteins purified from both serum and vitreous exhibited anti lipid peroxidation effect on erythrocyte when added during in vitro assay of thiobarbuteric acid reactive substances (TBARS). In addition to this property the protein also has Fe2+sequestering effect. The anti TBARS activity of 88kDa protein was completely inhibited by 0.1mM concentration of parachlromercuric benzoate (PCMB) and 5,5′ dithiobis(2-nitrobenzoic acid) DTNB. The total thiol content (cysteine) of the purified 88kDa protein was found to be 8% by mass. Eighty eight kDa protein from both the sources namely vitreous and serum are immunologically identical when studied using polyclonal antibodies raised in goat against purified serum protein. The N terminal sequence of 88kDa protein by automated Edman’s degradation chemistry is A D D P N S L S P S A F A E A L A L L R D S X L A R F V. The protein and DNA data base search revealed no match to 88kDa protein and hence this was considered as unique protein. Further knowledge on the in vivo function of 88kDa protein is very important to understand its role in the pathogenesis of Eales’ disease.