Related ArticlesLow-affinity platelet factor 4 1H NMR derived aggregate equilibria indicate a physiologic preference for monomers over dimers and tetramers.
Biochemistry. 1991 Jan 29;30(4):925-34
Authors: Mayo KH
Low-affinity platelet factor 4 (LA-PF4), unlike another related, sequentially homologous (about 50%) platelet-specific protein, platelet factor 4 (PF4), is an active mitogenic and chemotactic agent. PF4 exhibits a high binding affinity for heparin, while LA-PF4 does not. Both PF4 and LA-PF4 can exist in dimer and tetramer aggregate states. Equilibrium constants for PF4 aggregation have recently been estimated from fractional populations derived from proton nuclear magnetic resonance (NMR) integrals assigned to resonances in monomer, dimer, and tetramer states [Mayo & Chen (1989) Biochemistry 28, 9469]. On a 500-MHz NMR time scale, relatively slow exchange among LA-PF4 aggregate species has also allowed Tyr 15 ring proton resonances to be assigned for monomer, dimer, and tetramer states in LA-PF4. As a function of pH and ionic strength, equilibrium association constants for LA-PF4 dimer (KD) and tetramer (KT) formation have been estimated from Tyr 15 ring proton resonance integrals. At low ionic strength, KD reaches a minimum value of 12 M-1 at pH 3 where KT is at its maximum value of 1.6 x 10(5) M-1. At pH 4.1, KD and KT have the same value, 1.1 x 10(3) M-1, which is the minimum value for KT. KD plateaus off to its maximum value of 2.2 x 10(4) M-1 by pH 5.5. These values are significantly lower than those for PF4. Analysis of the pH dependence of KD and KT suggests that electrostatic interactions probably among Glu/Asp and Lys/Arg side chains form the predominant force in the monomer-monomer binding process, i.e., KD, while like-charge repulsion due to proximal, intersubunit Glu/Asp residues decreases KT as the pH is raised. At pH 7 and low ionic strength, the dimer state is highly favored over the tetramer state. Elevating the solvent ionic strength at pH 7 destabilizes the dimer state. Under these more physiologic conditions, i.e., pH 7 and 0.1-0.2 M NaCl, LA-PF4 monomers are highly favored over dimers and tetramers. For PF4 under similar solvent conditions, tetramers predominate. Differences in biological activities between these homologous platelet-specific proteins may be the result, at least in part, of differing aggregation properties. The biologically active state for PF4 is tetramer, while for LA-PF4 it is monomer. Quaternary structure may, therefore, account for strong heparin binding in PF4, most likely by presenting a more favorable structural matrix for effective glycosaminoglycan interactions.
Human multiprotein bridging factor 1 and Calmodulin do not interact in vitro as confirmed by NMR spectroscopy and CaM-agarose affinity chromatography.
Human multiprotein bridging factor 1 and Calmodulin do not interact in vitro as confirmed by NMR spectroscopy and CaM-agarose affinity chromatography.
Human multiprotein bridging factor 1 and Calmodulin do not interact in vitro as confirmed by NMR spectroscopy and CaM-agarose affinity chromatography.
Protein Expr Purif. 2011 Jul 14;
Authors: Babini E, Hu X, Parigi G, Vignali M
The human multiprotein bridging factor 1 (hMBF1) has been established in different cellular types to have the role of transcriptional coactivator. It is also reported to be...
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[NMR paper] Perturbation of the conformational equilibria in Ras by selective mutations as studie
Perturbation of the conformational equilibria in Ras by selective mutations as studied by 31P NMR spectroscopy.
Related Articles Perturbation of the conformational equilibria in Ras by selective mutations as studied by 31P NMR spectroscopy.
FEBS Lett. 2004 Dec 17;578(3):305-10
Authors: Spoerner M, Wittinghofer A, Kalbitzer HR
Ras regulates a variety of different signal transduction pathways acting as molecular switch. It was shown by liquid and solid-state (31)P NMR spectroscopy that Ras exists in the...
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[NMR paper] Heparin binding to platelet factor-4. An NMR and site-directed mutagenesis study: arg
Heparin binding to platelet factor-4. An NMR and site-directed mutagenesis study: arginine residues are crucial for binding.
http://www.ncbi.nlm.nih.gov/corehtml/query/egifs/http:--www.pubmedcentral.nih.gov-corehtml-pmc-pmcgifs-pubmed-pmc.gif Related Articles Heparin binding to platelet factor-4. An NMR and site-directed mutagenesis study: arginine residues are crucial for binding.
Biochem J. 1995 Dec 1;312 ( Pt 2):357-65
Authors: Mayo KH, Ilyina E, Roongta V, Dundas M, Joseph J, Lai CK, Maione T, Daly TJ
Native platelet factor-4 (PF4) is an...
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[NMR paper] NMR solution structure of the 32-kDa platelet factor 4 ELR-motif N-terminal chimera:
NMR solution structure of the 32-kDa platelet factor 4 ELR-motif N-terminal chimera: a symmetric tetramer.
NMR solution structure of the 32-kDa platelet factor 4 ELR-motif N-terminal chimera: a symmetric tetramer.
Biochemistry. 1995 Sep 12;34(36):11399-409
Authors: Mayo KH, Roongta V, Ilyina E, Milius R, Barker S, Quinlan C, La Rosa G, Daly TJ
Native human platelet factor 4 (PF4) is a homotetrameric protein (70 residues/subunit) known for its anticoagulant heparin binding activity. 2D 15N--1H HSQC NMR experiments of native PF4 in solution...
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[NMR paper] Comparative studies of the interaction of human and bovine platelet factor 4 with hep
Comparative studies of the interaction of human and bovine platelet factor 4 with heparin using histidine NMR resonances as spectroscopic probes.
Related Articles Comparative studies of the interaction of human and bovine platelet factor 4 with heparin using histidine NMR resonances as spectroscopic probes.
J Protein Chem. 1993 Jun;12(3):303-9
Authors: Talpas CJ, Lee L
The pKa values of His-38 and His-50 of the heparin-binding protein, bovine platelet factor 4, are 5.6 and 6.5, respectively, as determined by 1H NMR spectroscopy. The 1H NMR...
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[NMR paper] Secondary structure of human granulocyte colony-stimulating factor derived from NMR s
Secondary structure of human granulocyte colony-stimulating factor derived from NMR spectroscopy.
http://www.ncbi.nlm.nih.gov/corehtml/query/egifs/http:--linkinghub.elsevier.com-ihub-images-PubMedLink.gif Related Articles Secondary structure of human granulocyte colony-stimulating factor derived from NMR spectroscopy.
FEBS Lett. 1992 Dec 21;314(3):435-9
Authors: Zink T, Ross A, Ambrosius D, Rudolph R, Holak TA
Recombinant 15N-, 13C-labeled human granulocyte colony-stimulating factor (rh-metG-CSF) has been studied by 2D and 3D NMR using...
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[NMR paper] 1H-NMR studies of bovine platelet factor 4: histidine assignments and interactions wi
1H-NMR studies of bovine platelet factor 4: histidine assignments and interactions with heparin.
Related Articles 1H-NMR studies of bovine platelet factor 4: histidine assignments and interactions with heparin.
Biochim Biophys Acta. 1991 Jun 24;1078(2):208-18
Authors: Talpas CJ, Walz DA, Lee L
1H-NMR spectroscopy has been used to assign and to characterize the two histidine C2H resonances of the heparin binding protein, bovine platelet factor 4. One histidine has a pKa value of 6.51 at 27 degrees C; the second histidine exhibits 2 pKa values...
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[NMR paper] Solution structures of human transforming growth factor alpha derived from 1H NMR dat
Solution structures of human transforming growth factor alpha derived from 1H NMR data.
Related Articles Solution structures of human transforming growth factor alpha derived from 1H NMR data.
Biochemistry. 1990 Aug 28;29(34):7805-13
Authors: Kline TP, Brown FK, Brown SC, Jeffs PW, Kopple KD, Mueller L
The 600-MHz 1H NMR spectrum of the des-Val-Val mutant of human transforming growth factor alpha (TGF-alpha) was reassigned at pH = 6.3. The conformation space of des-Val-Val TGF-alpha was explored by distance geometry embedding followed by...