Quantification of glycoprotein surface expression.

The expression levels of each mutant glycoprotein were measured using dual antibody staining on living cells, fluorescent microscopy and image analysis. Results included measurements from cell monolayers. They were obtained from triplicate measurements, from three separate experiments and expressed as intensity mean values for green and red pixels. Expression levels of each mutated protein was compared with that of the corresponding wild type (WT) protein (in bold). Differences in surface expression levels were not statistically significant (P > 0.05).