Molecular characterisation of a candidate gut sucrase in the pea aphid, Acyrthosiphon pisum.
The hydrolysis of sucrose, the principal dietary source of carbon for aphids, is catalysed by a gut alpha-glucosidase/transglucosidase activity. An alpha-glucosidase, referred to as APS1, was identified in both a gut-specific cDNA library and a sucrase-enriched membrane preparation from guts of the pea aphid Acyrthosiphon pisum by a combination of genomic and proteomic techniques. APS1 contains a predicted signal peptide, and has a predicted molecular mass of 68 kDa (unprocessed) or 66.4 kDa (mature protein). It has amino acid sequence similarity to alpha-glucosidases (EC 3.2.1.20) of glycoside hydrolase family 13 in other insects. The predicted APS1 protein contains two domains: an N-terminal catalytic domain, and a C-terminal hydrophobic domain. In situ localisation and RT-PCR studies revealed that APS1 mRNA was expressed in the gut distal to the stomach, the same localisation as sucrase activity. When expressed heterologously in Xenopus embryos, APS1 was membrane-bound and had sucrase activity. It is concluded that APS1 is a dominant, and possibly sole, protein mediating sucrase activity in the aphid gut.
Price
D R G
DR
Department of Biology, University of York, P.O. Box 373, York YO10 5YW, UK. d.r.g.price@durham.ac.uk <d.r.g.price@durham.ac.uk>
Karley
A J
AJ
Ashford
D A
DA
Isaacs
H V
HV
Pownall
M E
ME
Wilkinson
H S
HS
Gatehouse
J A
JA
Douglas
A E
AE
D000595:Amino Acid Sequence; D000818:Animals; D001042:Aphids / Q000201:enzymology*; D001483:Base Sequence; D015870:Gene Expression; D007422:Intestines / Q000201:enzymology; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D018532:Pisum sativum / Q000469:parasitology; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013393:Sucrase / Q000378:metabolism*; D000520:alpha-Glucosidases / Q000378:metabolism
D008565:Membrane Proteins; D000520:alpha-Glucosidases; D013393:Sucrase