Utilization of a peptide lead for the discovery of a novel PTP1B-binding motif.
Examination of the PTP1B inhibitory potency of an extensive series of phosphotyrosyl (pTyr) mimetics (Xxx) expressed in the EGFr-derived hexapeptide platform Ac-Asp-Ala-Asp-Xxx-Leu-amide previously led to the finding of high inhibitory potency when Xxx = 4-(phosphonodifluoromethyl)phenylalanyl (F2Pmp) (K(i) = 0.2 microM) and when Xxx = 3-carboxy-4-carboxymethyloxyphenylalanyl (K(i) = 3.6 microM). In the first instance, further work led from the F2Pmp-containing peptide to monomeric inhibitor, 6-(phosphonodifluoromethyl)-2-naphthoic acid (K(i) = 22 microM), and to the pseudo-dipeptide mimetic, N-[6-(phosphonodifluoromethyl)-2-naphthoyl]-glutamic acid (K(i) = 12 microM). In the current study, a similar approach was applied to the 3-carboxy-4-carboxymethyloxyphenylalanyl-containing peptide, which led to the preparation of monomeric 5-carboxy-6-carboxymethyloxy-2-naphthoic acid (K(i) = 900 microM). However, contrary to expectations based on the aforementioned F2Pmp work, incorporation of this putative pTyr mimetic into the pseudo-dipeptide, N-[5-carboxy-6-carboxymethyloxy-2-naphthoyl]-glutamic acid, resulted in a substantial loss of binding affinity. A reevaluation of binding orientation for 5-carboxy-6-carboxymethyloxy-2-naphthoic acid was therefore undertaken, which indicated a 180 degrees reversal of the binding orientation within the PTP1B catalytic site. In the new orientation, the naphthyl 2-carboxyl group, and not the o-carboxy carboxymethyloxy groups, mimics a phosphoryl group. Indeed, when 5-carboxy-2-naphthoic acid itself was examined at neutral pH for inhibitory potency, it was found to have K(i) = 31 +/- 7 microM, which is lower than parent 5-carboxy-6-carboxymethyloxy-2-naphthoic acid. In this fashion, 5-carboxy-2-naphthoic acid (or more appropriately, 6-carboxy-1-naphthoic acid) has been identified as a novel PTP1B binding motif.
Gao
Y
Y
Laboratory of Medicinal Chemistry, Center for Cancer Research, National Cancer Institute, NCI-Frederick, Bldg. 376, Boyles Street, Frederick, Maryland 21702, USA.
Voigt
J
J
Zhao
H
H
Pais
G C
GC
Zhang
X
X
Wu
L
L
Zhang
Z Y
ZY
Burke
T R
TR
D020134:Catalytic Domain; D004791:Enzyme Inhibitors / Q000737:chemistry*; D006801:Humans; D008958:Models, Molecular; D008968:Molecular Conformation; D018716:Molecular Mimicry; D009281:Naphthalenes / Q000138:chemical synthesis* / Q000737:chemistry; D009842:Oligopeptides / Q000138:chemical synthesis* / Q000737:chemistry; D011485:Protein Binding; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors* / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry
D004791:Enzyme Inhibitors; D009281:Naphthalenes; D009842:Oligopeptides; D011994:Recombinant Proteins; C516607:PTPN1 protein, human; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases