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Bucci JC, McClintock CS, Chu Y, Ware GL, McConnell KD, Emerson JP, Peterson CB. Resolving distinct molecular origins for copper effects on PAI-1. J Biol Inorg Chem 2017; 22:1123-1135. [PMID: 28913669 PMCID: PMC5613068 DOI: 10.1007/s00775-017-1489-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2017] [Accepted: 08/24/2017] [Indexed: 11/19/2022]
Abstract
Components of the fibrinolytic system are subjected to stringent control to maintain proper hemostasis. Central to this regulation is the serpin plasminogen activator inhibitor-1 (PAI-1), which is responsible for specific and rapid inhibition of fibrinolytic proteases. Active PAI-1 is inherently unstable and readily converts to a latent, inactive form. The binding of vitronectin and other ligands influences stability of active PAI-1. Our laboratory recently observed reciprocal effects on the stability of active PAI-1 in the presence of transition metals, such as copper, depending on the whether vitronectin was also present (Thompson et al. Protein Sci 20:353–365, 2011). To better understand the molecular basis for these copper effects on PAI-1, we have developed a gel-based copper sensitivity assay that can be used to assess the copper concentrations that accelerate the conversion of active PAI-1 to a latent form. The copper sensitivity of wild-type PAI-1 was compared with variants lacking N-terminal histidine residues hypothesized to be involved in copper binding. In these PAI-1 variants, we observed significant differences in copper sensitivity, and these data were corroborated by latency conversion kinetics and thermodynamics of copper binding by isothermal titration calorimetry. These studies identified a copper-binding site involving histidines at positions 2 and 3 that confers a remarkable stabilization of PAI-1 beyond what is observed with vitronectin alone. A second site, independent from the two histidines, binds metal and increases the rate of the latency conversion.
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Affiliation(s)
- Joel C Bucci
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Walters Life Sciences Building, 1414 Cumberland Avenue, Knoxville, TN, 37996, USA.,Department of Biological Sciences, A221 Life Sciences Annex, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Carlee S McClintock
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Walters Life Sciences Building, 1414 Cumberland Avenue, Knoxville, TN, 37996, USA
| | - Yuzhuo Chu
- Department of Biological Sciences, A221 Life Sciences Annex, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Gregory L Ware
- Department of Biological Sciences, A221 Life Sciences Annex, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Kayla D McConnell
- Department of Chemistry, Mississippi State University, Box 1115, Starkville, MS, 39762, USA
| | - Joseph P Emerson
- Department of Chemistry, Mississippi State University, Box 1115, Starkville, MS, 39762, USA
| | - Cynthia B Peterson
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Walters Life Sciences Building, 1414 Cumberland Avenue, Knoxville, TN, 37996, USA. .,Department of Biological Sciences, A221 Life Sciences Annex, Louisiana State University, Baton Rouge, LA, 70803, USA.
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Nettles WL, Song H, Farquhar ER, Fitzkee NC, Emerson JP. Characterization of the Copper(II) Binding Sites in Human Carbonic Anhydrase II. Inorg Chem 2015; 54:5671-80. [PMID: 26010488 PMCID: PMC4482258 DOI: 10.1021/acs.inorgchem.5b00057] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Human carbonic anhydrase (CA) is a well-studied, robust, mononuclear Zn-containing metalloprotein that serves as an excellent biological ligand system to study the thermodynamics associated with metal ion coordination chemistry in aqueous solution. The apo form of human carbonic anhydrase II (CA) binds 2 equiv of copper(II) with high affinity. The Cu(2+) ions bind independently forming two noncoupled type II copper centers in CA (CuA and CuB). However, the location and coordination mode of the CuA site in solution is unclear, compared to the CuB site that has been well-characterized. Using paramagnetic NMR techniques and X-ray absorption spectroscopy we identified an N-terminal Cu(2+) binding location and collected information on the coordination mode of the CuA site in CA, which is consistent with a four- to five-coordinate N-terminal Cu(2+) binding site reminiscent to a number of N-terminal copper(II) binding sites including the copper(II)-amino terminal Cu(2+) and Ni(2+) and copper(II)-β-amyloid complexes. Additionally, we report a more detailed analysis of the thermodynamics associated with copper(II) binding to CA. Although we are still unable to fully deconvolute Cu(2+) binding data to the high-affinity CuA site, we derived pH- and buffer-independent values for the thermodynamics parameters K and ΔH associated with Cu(2+) binding to the CuB site of CA to be 2 × 10(9) and -17.4 kcal/mol, respectively.
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Affiliation(s)
- Whitnee L. Nettles
- Mississippi State University: Department of Chemistry Box 9573 Mississippi State University Mississippi State, MS 39762-9573
| | - He Song
- Mississippi State University: Department of Chemistry Box 9573 Mississippi State University Mississippi State, MS 39762-9573
| | - Erik R. Farquhar
- Case Western Reserve University Center for Synchrotron Biosciences, National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Nicholas C. Fitzkee
- Mississippi State University: Department of Chemistry Box 9573 Mississippi State University Mississippi State, MS 39762-9573
| | - Joseph P. Emerson
- Mississippi State University: Department of Chemistry Box 9573 Mississippi State University Mississippi State, MS 39762-9573
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