Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2001
Publication Date: N/A
Interpretive Summary: In this work we examine the aminophospholipid architecture of the bovine erythrocyte, which are asymmetrically distributed in the inner and outer layer of erythrocyte membrane. We postulate an enzymatic mechanism that may account for the observed asymmetrical phospholipid distribution. The results are relevant to the biology of tick-transmitted hemoparasites and ricketsias such as Babesia bovis, B. bigemina and A. marginale that invade and replicate in mature bovine erythrocytes.
Technical Abstract: Ruminant erythrocytes are remarkable for their choline-phospholipid anomalies; namely, low or absent phosphatidylcholine (PC) along with high sphingomyelin levels. Here, we report another anomaly in bovine erythrocytes that affects aminophospholipids: phosphatidylethanolamine (PE) shows an extreme asymmetry, with only 2% of the total present in the outer leaflet. Furthermore, we found that phospholipase A(2), an enzyme located on the external surface of the erythrocytes, shows higher activity against PC than against PE. In addition, we observed that acylation of PE is by far the most important biosynthetic event in this system. We propose that deacylation of PE and PC by phospholipase A(2) to generate lysocompounds, followed by selective reacylation of lyso-PE in the inner leaflet, can account for the compositional and architectural peculiarities of bovine erythrocyte membranes