Localization of binding sites of F-protein (phosphofructokinase) on the myosin molecule

Summary To determine the location of F-protein binding sites on myosin, the interaction of F-protein with myosin and its proteolytic fragments in 0.1 m KCl,10 mm potassium phosphate, pH 6.5, has been investigated using sedimentation, electron microscopy and optical diffraction methods.Sedimentation experiments show that F-protein can bind to myosin and myosin rod rather than to light meromyosin or subfragment-1. The F-protein binding to myosin and rod is of a similar character. The calculated values of the constants of F-protein binding to myosin and rod are 2.6 × l0⁵M^–1 and 2.1 × 10⁵ m^–1, respectively. The binding sites are probably located on the subfragment-2 portion of the myosin molecule. The number of the F-protein binding sites calculated per chain weight of 80 000 is 5 ±1.Electron microscopic observations confirm the sedimentation results. F-protein does not bind to light meromyosin paracrystals, but decorates myosin and rod filaments with the interval of 14.3 nm regardless of whether F-protein is added prior to or after filamentogenesis. The comparison of optical diffraction patterns obtained from myosin and rod filaments with those from decorated ones reveals the marked enhancement of meridional reflection at (14.3 nm)^–1 in the latter case.Neither the increase in ionic strength from 0.1 to 0.15 and pH from 6.5 to 7.3 nor substitution of potassium phosphate buffer by imidazole-HCl buffer, or Tris-HCl influences F-protein binding to myosin and rod filaments as visualized by electron microscopy.The possible significance of F-protein location in the thick filament structure is discussed.     

Total Parathyroidectomy With Autotransplantation in Haemodialysed Patients With Secondary Hyperparathyroidism--Should It Be Abandoned?

The development of secondary hyperparathyroidism is almost universalin patients with end-stage renal disease. Medical managementfrequently fails and in such circumstances parathyroidectomybecomes a necessity. Total parathyroidectomy with autotransplantationof parathyroid tissue into the patient's forearm has been advocatedas the surgical procedure of choice. In a previous publicationwe reported our experience with this technique in six haemodialysedpatients. We now extend our follow-up to 19 patients over anobservation period ranging from 6 to 66 months. Five of thesepatients required graft removal because of recurrent secondaryhyperparathyroidism. Despite total graft removal, two patientshad clinical and laboratory evidence of persistent hyperparathyroidism.Histology of the removed graft tissue demonstrated severe hyperplasiaas well as invasion of adjacent muscle, adipose tissue, andvascular channels by parathyroid cells. This raises the possibilityof local and distant metastatic spread of parathyroid tissueresulting in hyperparathyroidism. We suggest that parathyroidautotransplantation is potentially hazardous and should in factbe abandoned.     

PATHOGENESIS OF EXTRINSIC ALLERGIC ALVEOLITIS AND PULMONARY FIBTOSIS INDUCED BY STREPTOMYCES THERMOHYGROSCOPICUS

There were 48 strains of thermophilic actinomyces isolated from the specimens of mouldy hay and sputum of the patients suffering from farmer’s lung (FL). Streptomyces thermohygroscopicus (STHs),one strain of them, was used for this investigation. The microorganisms were injected into the lungs of rabbits and rats by thyrocrico – or tracheocentesis. The result showed that the pathological changes in the lungs including macrophage alveolitis, granuloma formation and diffuse interstitial were similar to that induced by other thermophilic actinomyces. IgG and C3 deposition in the lesions were also observed by immunofluorescence examination. Specific immunocomplexes in the sera of some animals were detected by ELISA with the STHs was possibly one of the pathogens responsible for FL in China’s countryside.