Q. The two vesicle fractions are either untreated (-) or are incubated with the protease trypsin (+). The membrane vesicles are next washed, the membranes solubilized and the proteins denatured and analyzed by SDS gel electrophoresis and Western blotting using polyclonal antibodies against glycophorin A, an erythrocyte plasma membrane protein. The subsequent data are obtained:

What could be deduced from these data about the structure of glycophorin A