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The Use of 4-(2-pyridylazo)resorcinol in Studies of Zinc Release From Escherichia Coli Aspartate Transcarbamoylase

The Use of 4-(2-pyridylazo)resorcinol in Studies of Zinc Release From Escherichia Coli Aspartate Transcarbamoylase

J B Hunt, S H Neece, A Ginsburg

Anal Biochem. 1985 Apr;146(1):150-7.

PMID: 3887984

Abstract:

The metallochromic indicator 4-(2-pyridylazo)resorcinol (PAR) has been used at pH 7.0 to monitor the mercurial-promoted Zn2+ release from Escherichia coli aspartate transcarbamoylase and Zn2+ uptake by regulatory dimers upon displacement of the mercurial reagent with 2-mercaptoethanol. The release of Zn2+ (as reflected by a yellow to orange color change in PAR solutions) is linked to dissociation of the enzyme since the six Zn2+ bonding domains stabilize catalytic and regulatory chain contacts; the rebinding of Zn2+ produces enzyme assembly and a corresponding decrease in the amount of PAR-Zn2+ complex. Using greater than 10-fold PAR to free Zn2+ at pH 7.0, delta epsilon = 6.6 +/- 0.2 X 10(4) M-1 cm-1 at 500 nm (20 degrees C) for (PAR)2Zn2+ complex formation (beta'2 approximately equal to 10(12) M-1). In kinetic studies at pH 7.0, PAR (10(-4) M) has been used to measure the instantaneous concentration of Zn2+ released from micromolar quantities of protein; second-order k = 2 X 10(7) M-1 s-1 for forming the 1:1 PAR:Zn2+ complex. These properties of PAR-Zn2+ interactions make PAR a generally useful reagent for studying Zn2+ release from proteins.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP1141599	4-(2-Pyridylazo)resorcinol		1141-59-9	Price

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