Human platelet factor 4 monomer-dimer-tetramer equilibria investigated by sup 1 H NMR spectroscopy

Journal Article · Tue Nov 28 04:00:00 EST 1989 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00450a034· OSTI ID:6854955

Mayo, K H; Chen, M J ^[1]

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1. Temple Univ., Philadelphia, PA (USA)

As a function of protein concentration, proton NMR spectra of human platelet factor 4 (PF4) differ. Correlation with low-angle laser light scattering data has allowed identification of concentration-dependent NMR spectral changes to PF4 aggregation, with tetramers being the largest aggregates formed. Well-resolved aromatic ring proton NMR resonances were assigned to Tyr-60, His-I, and His-II in monomer, dimer, and tetramer states. Since Tyr-60, 3,5 ring proton resonances are well resolved from state to state, estimation of fractional populations in each state was possible. By varying the PF4 concentration, changes in these populations when plotted according to the Hill equation show a bimolecular mechanism of aggregation which proceeds from monomers to tetramers through a dimer intermediate. Equilibrium constants for dimer association (K{sub D}) and tetramer association (K{sub T}) have been estimated as a function of pH and ionic strength. Increasing the solvent ionic strength stabilizes the tetramer state especially at low pH, suggesting that intersubunit, repulsive electrostatic interactions probably between/among cationic side chains (Lys/Arg) attenuate the aggregation process. Information based primarily on histidine pK{sub a} values and photo-CIDNP {sup 1}H NMR data suggests that Tyr-60 and His-I, but not His-II, are significantly affected by the aggregation process.

• OSTI ID: 6854955
• Journal Information: Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 28:24; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
AMINO ACIDS
ANIMALS
AZOLES
BARYONS
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BLOOD COAGULATION FACTORS
BLOOD PLATELETS
BODY FLUIDS
CARBOXYLIC ACIDS
CHEMICAL SHIFT
COAGULANTS
DRUGS
ELEMENTARY PARTICLES
FERMIONS
HADRONS
HEMATOLOGIC AGENTS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HISTIDINE
HYDROXY ACIDS
IMIDAZOLES
KINETICS
MAGNETIC RESONANCE
MAMMALS
MAN
MATERIALS
NUCLEAR MAGNETIC RESONANCE
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OVERHAUSER EFFECT
PEPTIDES
PH VALUE
PRIMATES
PROTEINS
PROTONS
REACTION KINETICS
RESONANCE
TYROSINE
VERTEBRATES