Fluorometric studies on the light chains of skeletal muscle myosin. III. Effect of Ca2+ on the reactivity of two SH groups of DTNB light chain in myosin and in the isolated state

We studied the effect of Ca2+ on the reactivities of two SH groups of DTNB light chain (Cys 128 and Cys 157) using a fluorogenic thiol reagent. It was found that a Ca2+-induced change in reactivity occurred only with Cys 128 when the light chain was in an isolated state, whereas it occurred with both Cys 128 and Cys 157 when the light chain was incorporated in myosin. These results indicate that the Ca2+-induced change in the conformation of DTNB light chain in the isolated state was different from that of the light chain in myosin. It may therefore be difficult to relate the Ca2+-induced conformational change observed in the isolated DTNB light chain to the molecular mechanism of myosin-linked Ca2+ regulation.

Gastric pepsin and acid secretion following various operations for gastric and duodenal ulcer

In 117 cases of gastric and duodenal ulcer subjected to various types of operation, insulin- and histamine-stimulated secretion of gastric pepsin and acid was investigated at follow-up. Secretory responses of gastric pepsin to the stimulation with insulin and histamine were different from those of gastric acid. Insulin was confirmed to have a greater ability than histamine to stimulate gastric pepsin secretion. In the cases of vagotomy with pyloroplasty and those of vagotomy with hemigastrectomy, the average reduction rates of peak pepsin output were 80% and 92%, respectively, after insulin-stimulation, and 52% and 74% after histamine-stimulation. In view of gastric pepsin secretion, pylorus-preserving gastrectomy and segmental gastrectomy are more physiological than distal gastrectomy.

Study on histogenesis of pelvic endometriosis

The histogenesis of pelvic endometriosis can not be sufficiently accounted for by a single theory. Thus it may be necessary to pressure plural theories for the explanation of their histogenesis. On collected 253 cases of endometriosis, some clinical and pathological studies were carried out and classified to adenomyosis (A) 37%, ovarian and pelvic endometriosis (O.P) 17%, and others (A+O.P) 45%. Age of the group O.P adenomyosis (A) 37%, ovarian and pelvic endometriosis (O.P) 17%, and others (A+O.P) 45%. Age of the group O.P tended to be younger, as compared with other groups. Pathological study revealed that in group (A+O.P), the lesion tended to be younger, as compared with other groups. Pathological study revealed that in group (A+O.P), the lesion in uterine wall was extensive and deep proliferation in many cases, and it was frequently more at least than group A. Especially, it is necessary to distinguish from each other two different cases which showed endometriosis in the ovary and pelvic peritoneum, that is, to distinguish them by the presence or absence of adenomyosis. In the case of group O.P complicated by A, it is thought highly probable that discrete dissemination may take place from the foci of adenomyosis. In the case of group O.P there may be sufficient room for the application of the Sampson's theory or metaplastic theories. In view of conspicuous trait in the age, however, the possibility of lymphogenous dissemination of endometriosis may be valuable.

Involvement of 17K dalton light chain of smooth muscle myosin in substrate-induced conformational change

Conformational changes of the region involving 17K dalton light chain (G2) in gizzard myosin induced by ATP and its analogs were studied by a combination of light chain exchange and fluorescence spectroscopy. The cysteinyl residues of myosin light chain mixture, 20K dalton G1 and 17K dalton G2 chain, were labeled with a fluorescent thiol reagent, N-(1-anilionon-aphthyl-4ymaleimide (ANM). Chicken gizzard myosin was incubated with a large excess of the fluorescence labeled exogenous light chains in 2 M urea. After removal of urea and unbound light chains, a strong fluorescent band was observed at the position of the 17K dalton light chain (G2) of myosin on SDS PAGE. There was no difference in enzymatic activity and light chain composition between myosins before and after light chain exchange. The emission spectrum of ANM label in 17K dalton light chain in the bound state in myosin showed a fluorescence enhancement and a blue shift on adding ATP but not ADP. The spectral change disappeared after conversion of ATP to ADP. Various nucleoside triphosphates other than ATP had similar effects on the fluorescence spectrum. The relative effectiveness of most nucleotides on the fluorescence spectral change of ANM in the light chain bound in myosin agreed well with that on tryptophan residues in myosin, except in the case of ADP and CTP. These results suggest that 17K dalton light chain of gizzard myosin is closely related to the ATPase site of myosin.

Interaction of myosin subfragment-1 with actin. II. Location of the actin binding site in a fragment of subfragment-1 heavy chain

The heavy chain of subfragment-1 prepared by chymotrypsin treatment had a molecular weight of about 96K. The heavy chain was split into 26 K, 50 K, and 21 K fragments by trypsin. When the trypsin-treated subfragment-1 was cross-linked with dimethyl suberimidate, cross-linked products of 26 K, 50 K, and 21 K fragments and of 50 K and 21 K fragments appeared, but there was little cross-linked product of 26 K and 50 K fragments or of 26 K and 21 K fragments. When the cross-linking experiments were carried out in the presence of actin, a new band appeared and the amount of cross-linked product of 26 K, 50 K, and 21 K fragments decreased by about 50%. The molecular weight of the new band was lower than that of the cross-linked product of 26 K, 50 K, and 21 K fragments, and higher than that of the dimer of actin. Based on this and some other results, we suggest that this band represented a cross-linked product of actin and the 50 K fragment. We also suggest that the decrease in the amount of cross-linked product of 26 K, 50 K, and 21 K fragments reflected the conformational change in subfragment-1 due to the binding of actin.

Interaction of myosin subfragment-1 with actin. I. Effect of actin binding on the susceptibility of subfragment-1 to trypsin

The heavy chain of myosin subfragment-1 prepared by chymotrypsin treatment had a molecular weight of about 96 K. It was split into 26 K, 50K, and 21 K fragments on trypsin treatment. The effect of actin binding on the susceptibilities of the junctions between 26 K and 50 K and between 50 K and 21 K, and on that of alkali light chain 1 to trypsin was studied. The addition of actin increased the viscosity of the solution, and the apparent activity of trypsin decreased. We estimated this decrease as 35% by measuring the degradation of gamma-globin heavy chain, which is known not to interact with actin and subfragment-1 but is known to be susceptible to trypsin, in actin-subfragment-1 solution. Taking this value into consideration, we concluded that the 26 K-50 K junction became 5 times more and the 50 K-21 K junction became 3 times less susceptible to tryptic attack upon the binding of actin. We also observed that alkali light chain 1 became resistant to trypsin upon the binding of actin to subfragment-1. The relation between this conformational change in subfragment-1 and the cyclic interaction of subfragment-1 with actin and ATP is discussed.

Interaction of myosin subfragment-1 with actin. III. Effect of cleavage of the subfragment-1 heavy chain on its interaction with actin

To determine the reason why the Mg2+-ATPase activity of subfragment-1 prepared with chymotrypsin was activated more by actin than that of subfragment-1 prepared with trypsin was and the reason why the former could enhance the polymerization of actin and the latter could not, we digested subfragment-1, prepared with chymotrypsin, with trypsin and examined the actin activated Mg2+-ATPase activity and the ability to polymerize actin. It was found that cleavage of the heavy chain decreased the actin activated Mg2+-ATPase activity of subfragment-1 prepared with chymotrypsin but did not affect its ability to polymerize actin. Trypsin attacked the subfragment-1 heavy chain at two sites and produced 26 K, 50 K, and 21 K fragments. From the comparison of the time course of tryptic digestion with that of the decrease in actin activation, it was deduced that cleavage of the 50 K-21 K junction was mainly responsible for the decrease in actin activation. We also measured the length and the amount of F-actin polymerized by the addition of different amounts of subfragment-1. It was found that the amount of F-actin increased with the increase in the amount of subfragment-1 added and that the length of F-actin also increased though slightly. We concluded from the results that subfragment-1 enhanced the polymerization not only by facilitating the nucleus formation but also by strengthening the bond between actin monomers in forming F-actin.

The histochemical distribution of protein bound sulfhydryl groups in human epidermis by the new staining method

Recently, we synthesized a new fluorescent thiol reagent, N-(7-dimethylamino-4-methylcoumarinyl)-maleimide (DACM) which is nonfluorescent by itself but will react readily with -SH groups to form highly fluorescent addition products. By the use of this reagent, we studied the localization and concentration of -SH groups and S--S linkages in the human epidermis. The distribution of -SH groups in living layers was abundant in cytoplasm but not in nuclei. The fluorescence was concentrated on the cell membrane or intercellular spaces (MIC parts) and was increased at the spino-granular junction. In the horny layer, the fluorescence of the MIC parts appeared brilliantly in the lower layers and decreased gradually. On the other hand, the fluorescence of cytoplasm in keratinized cells in the stratum corneum was faint. The localization of S--S linkages was not a characteristic of the living layers, but appeared abruptly at the junction of living and horny layers. The fluorescence was localized to the MIC parts and disappeared gradually. The distribution of S--S linkages appeared to be very low in the cytoplasm of keratinized cells. No substantial fluorescence was localized on keratohyalin granules even after reduction.

Fluorometric studies on conformational changes in tropomyosin associated with depolymerization

Spectrofluorometric studies on the conformational changes in tropomyosin associated with depolymerization of the molecules were carried out using 1-anilino-8-naphthalene sulfonate (ANS). When ANS-probed tropomyosin was depolymerized to its monomer, the fluorescence intensity markedly increased, with a decrease in fluorescence polarization. On the other hand, the emission maxima of the ANS-tropomyosin complexes of both forms were the same. The temperature dependence of the polarization of the complexes at various KCl concentrations suggested that the segmental motion of a moiety containing the fluorophore was considerably activated by depolymerization of tropomyosin. In the polymerized and oligomeric forms, a thermal transition in the polarization was observed with a transition temperature of 30 degrees C. Titration curves of tropomyosin with ANS showed simple saturation kinetics with both monomer and polymer, and the apparent dissociation constants were estimated to be 9.93 X 10(-5) M (monomer) and 7.43 X 10(-5) M (polymer). On the other hand, the number of the ANS-binding sites increased from 0.5 to 2.0 per tropomyosin monomer on depolymerization of the molecules. Based on these results, the conformational state of tropomyosin in the polymerized form is discussed.

Studies on calcium ion-induced conformation changes in the actin-tropomyosin-troponin system by fluorimetry. IV. Conformational changes in the region containing fluorescence-labeled sulfhydryl group(s) of troponin

Conformational changes associated with the functional states of the molecule of troponin were studied using SH-direct fluorogenic reagents, N-(p-(2-benzimidazolyl)phenyl) maleimide (BIPM) and N-(1-anilinonaphthyl-4) maleimide (ANM). 1. The fluorescence parameters of ANM-troponin, intensity, and polarization, did not change on combining it with tropomyosin alone, but markedly changed when F-actin was further added to the system. 2. The conformation around the dye-labeled sulfhydryl group(s) was shown to be susceptible to Ca2+ in terms of fluorescence intensity of the label, thermal transition of the conformation, and the microenvironment near the label. 3. On addition of Ca2+, the fluorescence characteristics of the two systems, ANM-troponin . tropomyosin and ANM-troponin . tropomyosin . F-actin complexes, were altered in opposite directions. When BIPM was used in place of ANM, similar changes were observed: a simple decrease in the intensity when pCa was decreased from 7.4 to 5.5 in the system without F-actin and a sigmoidal increase in the range from pCa 7 to 6 in the system with F-actin. Heavy meromyosin, when added to the latter complex (the reconstituted thin filaments), made the profile of its Ca2+ concentration dependence of fluorescence similar to that of the former complex. When tropomyosin was labeled in place of troponin, similar results were obtained. The data obtained imply that the Ca2+-induced conformational changes of troponin are markedly modified when detached from actin, and that heavy meromyosin weakens the interaction of the troponin . tropomyosin complex with F-actin.

Study on calcium transport by sarcoplasmic reticulum vesicles using fluorescence probes

Fluorescence changes of 1-anilino-8-naphthalenesulfonic acid and 3,3'-dipropyl-2,2'-thiadicarbocyanine during Ca transport by sarcoplasmic reticulum vesicles were studied. The fluorescence of both probes is enhanced corresponding to the rapid initial Ca uptake. The enhancement could be interpreted in terms of increased binding of the former (anionic) dye and decreased binding of the latter (cationic) dye to the vesicles, suggesting a change in the surface charge of the membranes associated with Ca transport. Under limited conditions where Na, K, and Mg were not added exogenously, Ca could be transported without concomitant counter-transport of these cations.

Immune adherence: a quantitative and kinetic analysis

Quantitative and kinetic analysis of the immune-adherence reaction (IA) between C3b fragments and IA receptors as an agglutination reaction is difficult. Analysis is possible, however, by use of radio-iodinated bovine serum albumin as antigen at low concentrations (less than 200 ng/ml) and optimal concentration of antibody to avoid precipitation of antigen--antibody complexes with human erythrocytes without participation of complement. Antigen and antibody are reacted at 37 degree C, complement is added, the mixture incubated and human erythrocytes added; after further incubation, ice-cold EDTA containing buffer is added and the erythrocytes centrifuged and assayed for radioactivity. Control cells reacted with heated guinea pig serum retained less than 5% of the added radioactivity. The method facilitates measurement of IA reactivity and permits more detailed analysis of the mechanism underlying the reaction.

Effects of tryptic digestion on the enzymatic activites of chicken gizzard myosin

Tryptic digestion of gizzard myosin resulted in the degradation of the 20K light chain (G1) to its 17K fragment, which could not be phosphorylated. The rapid loss of Ca2+-dependent activation of actomyosin ATPase activity accompanied the degradation of G1. Increase in the Ca2+-ATPase activity and decrease in the EDTA-ATPase activity of myosin accompanied the degradation of myosin heavy chain, but not the cleavage of G1.

A novel fluorometric ultramicro determination of serum leucine aminopeptidase using a coumarine derivative

A simple and rapid rate assay of serum leucine aminopeptidase is described, using a novel fluorogenic substrate, 7-L-leucyl-4-methylcoumarinylamide. The reaction is initiated by adding 10 microliter of serum, and the fluorescence development for 1 min due to the 7-amino-4-methylcoumarin liberated at 37 degrees C is followed directly on a recorder. The proposed method is proved to be free from error due to the adsorption of the substrate dye to serum albumin and to be applicable to hyperbilirubinemic sera by simple correction. The values obtained by this method showed good correlation with those obtained by the conventional method of Goldbarg and Rutenberg (Goldbarg, J.A. and Rutenberg, A.M. (1958) Cancer 11, 283-291).