Association of midgut defensin with a novel serine protease in the blood-sucking fly Stomoxys calcitrans.
Using ELISA we provide direct evidence that the midgut defensins of the blood-sucking fly Stomoxys calcitrans are secreted into the gut lumen. We show that midgut defensin peptide levels increase up to fortyfold in response to a blood meal but not to a sugar meal. The data suggests the midgut defensin genes are post-transcriptionally regulated and that their function is protection of the stored blood meal from bacterial attack while it awaits digestion. Using recombinant defensins produced in Pichia pastoris we demonstrate that while in the gut cells the midgut defensins are bound in an SDS-stable complex to proteins with an apparent molecular weight of > 26 kDa from which they are released when secreted into the gut lumen. This > 26 kDa protein (Ssp3) has been cloned and sequenced and is a member of the serine protease S1 family with homologies to multiple insect proteases and to vertebrate trypsins and elastases.
Hamilton
J V
JV
School of Biological Sciences, University of Wales, Bangor UK.
Munks
R J L
RJ
Lehane
S M
SM
Lehane
M J
MJ
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D003429:Cross Reactions; D018076:DNA, Complementary; D023082:Defensins / Q000235:genetics / Q000378:metabolism*; D004064:Digestive System; D008969:Molecular Sequence Data; D009117:Muscidae / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D012967:Sodium Dodecyl Sulfate
D018076:DNA, Complementary; D023082:Defensins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D012967:Sodium Dodecyl Sulfate; D012697:Serine Endopeptidases; C460219:Stomoxys serine protease 3