Dm. Quinn et al., CARBOHYDRATE-REACTIVE, PORE-FORMING OUTER-MEMBRANE PROTEINS OF AEROMONAS-HYDROPHILA, Infection and immunity, 62(9), 1994, pp. 4054-4058
Two outer membrane proteins of Aeromonas hydrophila A6, isolated in a
one-step affinity chromatography process based on carbohydrate reactiv
ity, were found to be pore-forming molecules in artificial planar bila
yer membranes. These carbohydrate-reactive outer membrane proteins (CR
OMPs; M,s, 40,000 and 43,000) were subjected to amino acid analysis. T
he amino acid profiles for these two outer membrane proteins were almo
st identical. A partial protein sequence of a 14-amino-acid fragment o
f the 40,000-Da protein revealed homology with outer membrane porins o
f Escherichia coli and A. hydrophila, CROMPs were compared with carboh
ydrate-reactive porins also extracted from outer membranes of A. hydro
phila A6, These porins were isolated by using standard porin purificat
ion techniques (insolubility in 2% sodium dodecyl sulfate, solubility
in 0.4 M NaCl, and Sephacryl S-200 gel filtration), and then Synsorb H
type 2 affinity chromatography was done. The physical and functional
properties of the carbohydrate-reactive porins and CROMPs were found t
o be identical. On the basis of pore-forming properties in planar lipi
d bilayers and channel inhibition with maltotriose solutions, a nonspe
cific, general diffusion porin and a LamB-like maltoporin were identif
ied in both CROMP and carbohydrate-reactive porin preparations. To our
knowledge, the use of carbohydrate reactivity to isolate channel-form
ing proteins from bacterial outer membranes has not been reported prev
iously.