Volume : 2, Issue : 4, APR 2016
EVOLUTION OF LYMPHOCYTES FROM PROTOZOA: THE HYPOTHESIS IS SUPPORTED BY THE SIMILARITY OF AMOEBAPORE AND GRANULYSIN
Alan S Coulson M.D, Angela F Coulson A. A.
It is a remarkable mystery as to why both primitive protozoa and mammalian lymphocytes employ similar proteins, to penetrate the membranes of bacteria with lethal consequences for the target. In the case of the protozoan Entamoeba histolytica the protein is called amoebapore; in the case of the human lymphocyte, it is the protein granulysin. Both of these proteins have the same basic structure based on the SAPLIP motif (saposin-like protein), a molecular arrangement conserved for billions of years. Not only that, but both proteins are designed to function in a similar way. They are thus both SAPLIP DEFENSE PROTEINS, and porcine NK-lysin similarly found in lymphocytes, provides a third example. The fact that SAPLIP DEFENSE PROTEINS (SDPs) are not present in other animal phyla (apart from platyhelminths), only deepens the mystery; and the 2 billion year gap between the first incarnation of the SDPs, and then their reappearance in mammalian lymphocytes, and no other tissue, not even macrophages leads us to think that protozoa were directly involved in the development of the lymphocyte, possibly to the extent of being direct ancestors. This hypothesis could be tested by finding SDPs in primitive fish.
LYMPHOCYTES, PROTOZOA, EVOLUTION, SAPLIPS, AMOEBAPORE, NK-LYSIN, GRANULYSIN.
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