Grafting of a High-Affinity Zn(II)-Binding Site on the .beta.-Barrel of Retinol-Binding Protein Results in Enhanced Folding Stability and Enables Simplified Purification

Biochemistry ◽  
1994 ◽  
Vol 33 (47) ◽  
pp. 14126-14135 ◽  
Author(s):  
Holger N. Mueller ◽  
Arne Skerra
Keyword(s):  
Binding Site ◽  
Binding Protein ◽  
Retinol Binding Protein ◽  
High Affinity ◽  
Beta Barrel

Characterization and mapping of the 12kDa FK506-binding protein (FKBP12)-binding site on different isoforms of the ryanodine receptor and of the inositol 1,4,5-trisphosphate receptor

2001 ◽  
Vol 354 (2) ◽  
pp. 413-422 ◽  
Author(s):  
Geert BULTYNCK ◽  
Patrick DE SMET ◽  
Daniela ROSSI ◽  
Geert CALLEWAERT ◽  
Ludwig MISSIAEN ◽  
...  
Keyword(s):  
Binding Site ◽  
Ryanodine Receptor ◽  
Binding Protein ◽  
Limited Proteolysis ◽  
Ip3 Receptor ◽  
Fk506 Binding Protein ◽  
High Affinity ◽  
Receptor Isoforms ◽  
Inositol 1,4,5 Trisphosphate ◽  
Affinity Interaction

We investigated the interaction of the 12kDa FK506-binding protein (FKBP12) with two ryanodine-receptor isoforms (RyR1 and RyR3) and with two myo-inositol 1,4,5-trisphosphate (IP3) receptor isoforms (IP3R1 and IP3R3). Using glutathione S-transferase (GST)-FKBP12 affinity chromatography, we could efficiently extract RyR1 (42±7% of the solubilized RyR1) from terminal cisternae of skeletal muscle as well as RyR3 (32±4% of the solubilized RyR3) from RyR3-overexpressing HEK-293 cells. These interactions were completely abolished by FK506 (20µM) but were largely unaffected by RyR-channel modulators. In contrast, neither IP3R1 nor IP3R3 from various sources, including rabbit cerebellum, A7r5 smooth-muscle cells and IP3R-overexpressing Sf9 insect cells from Spodoptera frugiperda, were retained on the GST-FKBP12 matrix. Moreover, immunoprecipitation experiments indicated a high-affinity interaction of FKBP12 with RyR1 but not with IP3R1. In order to determine the FKBP12-binding site, we fragmented both RyR1 and IP3R1 by limited proteolysis. We obtained a 45kDa fragment of RyR1 that bound to the GST-FKBP12 matrix, indicating that it retained all requirements for FKBP12 binding. This fragment was identified by its interaction with antibody m34C and must therefore contain its epitope (amino acids 2756–2803). However, no fragment of IP3R1 was retained on the column. These molecular data are in agreement with the lack of correlation between FKBP12 and IP3R1 expression in various cell types. The observation that FKBP12 did not affect IP3-induced Ca2+ release but reduced caffeine-induced Ca2+ release also indicated that mature IP3R1 and IP3R3, in contrast to RyR1 and RyR3, did not display a specific, high-affinity interaction with FKBP12.

Retinoid affinity label for the binding site of retinol-binding protein

Biochemistry ◽  
1982 ◽  
Vol 21 (8) ◽  
pp. 1899-1905 ◽  
Author(s):  
Mary Ann Gawinowicz ◽  
DeWitt S. Goodman
Keyword(s):  
Binding Site ◽  
Binding Protein ◽  
Retinol Binding Protein ◽  
Affinity Label

Film autoradiography identifies unique features of [125I]3,3'5'-(reverse) triiodothyronine transport from blood to brain

1994 ◽  
Vol 72 (1) ◽  
pp. 380-391 ◽  
Author(s):  
L. Y. Cheng ◽  
L. V. Outterbridge ◽  
N. D. Covatta ◽  
D. A. Martens ◽  
J. T. Gordon ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Choroid Plexus ◽  
Intravenous Administration ◽  
Binding Protein ◽  
Circumventricular Organs ◽  
Brain Parenchyma ◽  
Retinol Binding Protein ◽  
High Affinity ◽  
Reverse Triiodothyronine ◽  
The Brain

1. Steady-state iodothyronine profiles in plasma are composed of thyroid gland-synthesized hormones (mainly thyroxine) and tissue iodothyronine metabolites (mainly triiodothyronine and reverse triiodothyronine) that have entered the bloodstream. The hormones circulate in noncovalently bound complexes with a panoply of carrier proteins. Transthyretin (TTR), the major high-affinity thyroid hormone binding protein in rat plasma, is formed in the liver. It is also actively and independently synthesized in choroid plexus, where its function as a chaperone of thyroid hormones from bloodstream to cerebrospinal fluid (CSF) is undergoing close scrutiny by several groups of investigators. Because TTR has high-affinity binding sites for both thyroxine and retinol binding protein, its potential role as a mediator of combined thyroid hormone and retinoic acid availability in brain is of further interest. 2. While they are in the free state relative to their binding proteins, iodothyronines in the cerebral circulation are putatively subject to transport across both the blood-brain barrier (BBB) and choroid plexus CSF barrier (CSFB) before entering the brain. Previous autoradiographic studies had already indicated that after intravenous administration the transport mechanisms governing thyroxine and triiodothyronine entry into brain were probably similar, whereas those for reverse triiodothyronine were very different, although the basis for the difference was not established at that time. Intense labeling seen over brain ventricles after intravenous administration of all three iodothyronines suggested that all were subject to transport across the CSFB. 3. To evaluate the role of the BBB and CSFB in determining iodothyronine access to brain parenchyma, autoradiograms prepared after intravenous administration of [125I]-labeled hormones (revealing results of transport across both barriers) were compared with those prepared after intrathecal (icv) hormone injection (reflecting only their capacity to penetrate into the brain after successfully navigating the CSFB). 4. Those studies revealed that thyroxine and triiodothyronine were mainly transported across the BBB. They shared with reverse triiodothyronine a generally similar, limited pattern of penetration from CSF into the brain, with circumventricular organs likely to be the main recipients of iodothyronines (with or without retinol) transported across the CSFB. 5. Analysis of all of the images obtained after intravenous and icv hormone administration clarified the basis for the unique distribution of intravenously injected reverse triiodothyronine. The hormone is excluded by the BBB but may be subject to limited penetration into brain parenchyma via the CSF. 6. Overall the observations single out reverse triiodothyronine as the iodothyronine showing the most distinctive as well as the most limited pattern of transport from blood to brain.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Investigation of the forms of pig duodenal Ca2+-binding protein produced by limited tryptic hydrolysis

1986 ◽  
Vol 237 (3) ◽  
pp. 781-787 ◽  
Author(s):  
D T W Bryant ◽  
S Critch
Keyword(s):  
Binding Site ◽  
Binding Sites ◽  
Binding Protein ◽  
Native Protein ◽  
Binding Studies ◽  
High Affinity ◽  
C Terminus ◽  
Kd Values ◽  
T1 And T2 ◽  
Tryptic Hydrolysis

Vitamin D-dependent Ca2+-binding protein from pig duodenum was hydrolysed with trypsin in the presence of Ca2+ and two products were obtained: T1, which differed from the native protein by loss of Ac-Ser-Ala-Gln-Lys from the N-terminus and Ile-Ser-Gln-OH from the C-terminus, and T2, which differed from T1 by loss of a C-terminal lysine. The hydrolysis inactivated one of the two high-affinity Ca2+-binding sites on the native protein, and the remaining site was stable in T1 but labile in T2 when the proteins were Ca2+-free. Binding studies showed that T1 had Kd values of 2.8 +/- 0.1 nM, 57 +/- 13 microM and 0.8 +/- 0.3 microM for Ca2+, Mg2+ and Mn2+ respectively, and T2 had Kd 2.2 +/- 0.3 nM for Ca2+. The affinity for Mn2+, together with the other Kd values, identified the site on T1 as the site on the native protein previously found to have Kd 0.6 microM for Mn2+, rather than one with Kd 50 microM for Mn2+. In contrast with both the native protein and another form of the protein with a single Ca2+-binding site, the intrinsic fluorescence of T1 and T2 was little affected by the addition of Ca2+. It was concluded that the active binding site in T1 and T2, and also the site in the native protein with the higher affinity for Mn2+, was probably in the C-terminal half of the molecule.

scholarly journals Mechanisms of zinc binding to the solute-binding protein AztC and transfer from the metallochaperone AztD

2017 ◽  
Vol 292 (42) ◽  
pp. 17496-17505 ◽  
Author(s):  
Durga P. Neupane ◽  
Dante Avalos ◽  
Stephanie Fullam ◽  
Hridindu Roychowdhury ◽  
Erik T. Yukl
Keyword(s):  
Binding Site ◽  
Paracoccus Denitrificans ◽  
Binding Protein ◽  
Zinc Binding ◽  
Antibacterial Drug ◽  
Affinity Binding ◽  
Human Pathogens ◽  
High Affinity Binding ◽  
High Affinity ◽  
Flexible Loop

Bacteria can acquire the essential metal zinc from extremely zinc-limited environments by using ATP-binding cassette (ABC) transporters. These transporters are critical virulence factors, relying on specific and high-affinity binding of zinc by a periplasmic solute-binding protein (SBP). As such, the mechanisms of zinc binding and release among bacterial SBPs are of considerable interest as antibacterial drug targets. Zinc SBPs are characterized by a flexible loop near the high-affinity zinc-binding site. The function of this structure is not always clear, and its flexibility has thus far prevented structural characterization by X-ray crystallography. Here, we present intact structures for the zinc-specific SBP AztC from the bacterium Paracoccus denitrificans in the zinc-bound and apo-states. A comparison of these structures revealed that zinc loss prompts significant structural rearrangements, mediated by the formation of a sodium-binding site in the apo-structure. We further show that the AztC flexible loop has no impact on zinc-binding affinity, stoichiometry, or protein structure, yet is essential for zinc transfer from the metallochaperone AztD. We also found that 3 His residues in the loop appear to temporarily coordinate zinc and then convey it to the high-affinity binding site. Thus, mutation of any of these residues to Ala abrogated zinc transfer from AztD. Our structural and mechanistic findings conclusively identify a role for the AztC flexible loop in zinc acquisition from the metallochaperone AztD, yielding critical insights into metal binding by AztC from both solution and AztD. These proteins are highly conserved in human pathogens, making this work potentially useful for the development of novel antibiotics.

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