Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.1.52 (PNGase F)
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Time course digestion of intact human erythrocytes and right side-out vesicles with carboxypeptidase Y altered the Rh polypeptides and removed the 125I label that is normally incorporated by cell-surface radioiodination, but did not affect the RhD, Rhc, or RhE antigens. Under the same conditions, however, the LW antigens were rapidly destroyed. Digestion of inside-out and right side-out vesicles with aminopeptidase M was without any detectable effect on the Rh and LW antigens or polypeptides, although glycophorin A was degraded from right side-out but not from inside-out vesicles. These findings demonstrate that the C-terminal domain of the Rh and LW polypeptides is exposed at the external surface of human erythrocytes and indicate, in addition, that the LW antigens and tyrosine residue(s) of the LW and Rh proteins, respectively, are located close to the C termini of these polypeptides. Further studies using monoclonal and polyclonal antibodies showed that LW antigen expression is inhibited by treatment of red cells with EDTA and is selectively restored by Mg2+, but not by Mn2+ or Ca2+, whereas the Rh antigens were not affected under these conditions. In addition, O- and N-glycanase digestion of the LW glycoprotein removed its sugar chains, but did not alter significantly the epitopes recognized by the monoclonal anti-LW antibody.
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PMID:Surface orientation and antigen properties of Rh and LW polypeptides of the human erythrocyte membrane. 197 26

The RhD polypeptide and LW glycoprotein were separately immunopurified with monoclonal antibodies and compared by two-dimensional (2-D) iodopeptide mapping after digestion with alpha-chymotrypsin. These proteins have distinct 2-D maps, as seen after 125I-labeling tyrosine residues (chloramine-T procedure), and even more strikingly after labeling primary amine residues (Bolton-Hunter procedure). Of the more than 20 iodopeptides visualized, only five migrated identically when preparations of RhD and LW were directly compared, suggesting that RhD and LW are different proteins that may share some common protein domains. N-glycanase treatment of the iodopeptides did not modify the 2-D map of the RhD protein but greatly affected the LW map, further indicating that LW, but not RhD, carries N-linked carbohydrate chains. After deglycosylation the LW map was different from the RhD map, confirming that the RhD and LW polypeptides are different proteins. These findings demonstrate that LW is neither a glycosylated form of Rh protein nor is Rh a precursor of LW.
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PMID:Comparative analysis by two-dimensional iodopeptide mapping of the RhD protein and LW glycoprotein. 211 34

The major component immunoprecipitated from human red cell membranes by murine monoclonal antibodies (BS46 and BS56) against the LW blood group antigens is a 42,000 mol. wt glycoprotein. Upon digestion by an N-glycanase the LW component migrated as a 25,000 mol. wt component on SDS gels, whereas treatment by an O-glycanase led only to a small size reduction (2000). These data suggest that the LW glycoprotein might carry approximately eight to nine N-linked sugar chains and only a few (one or two) O-linked oligosaccharide chains. A minor component of 31,000 mol. wt was also identified in the LW immunoprecipitate. Preliminary analyses by two-dimensional peptide mapping indicate that the 31,000 mol. wt polypeptide is identical to authentic Rh proteins, therefore raising the possibility that the Rh and LW antigens are associated in the membrane as a functional complex called Rh cluster. Since the N-deglycosylated form of the LW and RhD proteins have different sizes (25,000 vs 31,000-32,000 respectively) and since their externally 125I-labelled domains have different two-dimensional peptide maps, it is concluded that LW is probably not a simple glycosylated form of the Rh proteins.
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PMID:Properties of the blood group LW glycoprotein and preliminary comparison with Rh proteins. 251 51