We have studied the ligand-binding reactions of lamprey (Petromyzon marinus and Petromyzon fluviatitis) hemoglobin with O2 and CO in the pH range 9.0 to 5.6 by means of both rapid reaction and equilibrium techniques. All the data can be accurately described by a model in which it is assumed that there are two forms of hemoglobin, a high affinity monomer and a lower affinity dimer, and that the ...

We used light scattering and ultracentrifugation to study the binding ratio of myosin and actin from normal and failing dog hearts and to determine the effect of temperature and adenosine triphosphate (ATP) on the binding. For comparison, similar studies were done on myosin and actin from rabbit skeletal muscle. We found a higher combining ratio, by weight, for cardiac myosin and actin (4.8 : 1...

The finding that exchange of tubulin subunits between tubulin dimers (alpha-beta + alpha'beta' <--> alpha'beta + alphabeta') does not occur in the absence of protein cofactors and GTP hydrolysis conflicts with the assumption that pure tubulin dimer and monomer are in rapid equilibrium. This assumption underlies the many physical chemical measurements of the K(d) for dimer dissociation. To resol...

The divalent cation binding properties of a protein which functions as a Ca2+-dependent regulator (CDR) of brain cyclic nucleotide phosphodiesterase and adenylate cyclase activities have been examined by equilibrium dialysis and circular dichroic spectrophotometry. The far-ultraviolet circular dichroic spectrum is characterized by negative maxima at 207 and 222 nm. Changes in the far-ultraviole...

The fluorescence of the cation auramine O was substantially enhanced by the presence of actin monomer. Titrations of this fluorescence enhancement indicated that actin monomer had two auramine O binding sites, each with a dissociation constant of approx. 20 microM. Calcium ions had no effect on the number of actin monomer-bound auramine O molecules or on the dissociation constant for that inter...