Aj. Cosgriff et al., A study of AroP-PheP chimeric proteins and identification of a residue involved in tryptophan transport, J BACT, 182(8), 2000, pp. 2207-2217
In vivo recombination has been used to make a series of AroP-PheP chimeric
proteins. Analysis of their respective substrate profiles and activities ha
s identified a small region within span III of AroP which can confer on a p
redominantly PheP protein the ability to transport tryptophan. Site-directe
d mutagenesis of the AroP-PheP chimera, PheP, and AroP has established that
a key residue involved in tryptophan transport is tyrosine at position 103
in AroP. Phenylalanine is the residue at the corresponding position in Phe
P. The use of PheP-specific antisera has shown that the inability of certai
n chimeras to transport any of the aromatic amino acids is not a result of
instability or a failure to be inserted into the membrane. Site-directed mu
tagenesis has identified two significant AroP-specific residues, alanine 10
7 and valine 114, which are the direct cause of loss of transport activity
in chimeras such as A152P. These residues replace a glycine and an alanine
in PheP and Bank a highly conserved glutamate at position 110. Some suggest
ions are made as to the possible functions of these residues in the tertiar
y structure of the proteins.