A study of an erythrocyte membrane protein that contributes to inhibition of agglutination of feline erythrocytes in glucose solution

概要

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Due to the negative charges on their surface membrane, erythrocytes usually do not agglutinate each other in vivo. However, when mixed with 5% glucose solution in a test tube, some feline erythrocytes exhibit agglutination. To investigate the reasons for this phenomenon, we extracted erythrocyte membrane proteins from these cells and subjected them to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In samples in which agglutination did not occur, a band was seen at the 36-kDa position, whereas in samples showing agglutination, this band disappeared or has lower intensity. The 36-kDa position corresponds to glycophorin A in the human erythrocyte membrane, but no immunochemical cross-reaction with this band was seen. We therefore conducted mass spectrometry in order to investigate the composition, and found a partial amino acid sequence, His-Ile-Thr-Ser-Tyr-Pro-Glu-Thr-His-Glu-Gly. Furthermore, although no protein showing this sequence was found in any database, this protein was confirmed to be an acidic glycoprotein, therefore it is thought to be a glycophorin-like molecule in the feline erythrocyte membrane that could contribute to inhibition of agglutination.