Escherichia coli Alkaline Phosphatase

Figure 5: The X-ray crystal structure of Escherichia coli AP. AP is a dimeric metalloenzyme with a total molecular weight of about 94 kDa.  It has three tryptophans per monomer, only one of which, tryptophan 109, has a long phosphorescence lifetime.

Figure 6: Close-up view of the hydrophobic core of AP around tryptophan 109.  A hydrogen bond is formed between glutamine 320 and the enamine of tryptophan 109 which stabilizes the indole ring.  The vicinity of tyrosine 84 makes it a candidate for collisional quenching of tryptophan 109ís phosphorescence.

Also shown is the close proximity of the phosphate and metal binding sites.

RTP Reports on Phosphate-Modulated Mg Binding to AP