Biomedical subjects
H Maruta
Publications and source records attributed to H Maruta.
'Cap 90', a 90-kDa Ca2+-dependent F-actin-capping protein from vertebrate brain.
A Ca2+-dependent actin filament-capping protein of 90 kDa was purified from bovine brain using a new and rapid isolation procedure. This basically includes affinity purification on DNase-I agarose. The protein caps the fast-growing end of actin filaments but has no fragmenting or severing activity. Using Triton X-100-extracted cytoskeletons, capping and severing activities of actin-binding proteins become clearly distinguishable from each other.
Ca2+-dependent actin-binding phosphoprotein in Physarum polycephalum. I. Ca2+/actin-dependent inhibition of its phosphorylation.
When crude extracts of the slime mold Physarum polycephalum were incubated with ATP and Mg2+ at 35 degrees C, a peptide of approximately 42,000 Da was predominantly phosphorylated. The kinase, separated from the phosphorylatable peptide, phosphorylated neither actin nor fragmin, both proteins of 42,000 Da, the latter known to cap and shorten actin filaments in a Ca2+-dependent manner. The phosphorylatable peptide was phosphorylated only at threonine residue(s), and its phosphorylation was almost completely inhibited by micromolar concentrations of Ca2+ in the extracts. The Ca2+-dependent inhibition of the phosphorylation was reversed by the subsequent addition of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid but not by trifluoperazine. The Ca2+-dependent inhibition of the phosphorylation required either actin or another, so far unidentified, protein(s) which is distinct from calmodulin. Fragmin reversed the Ca2+/actin-dependent inhibition of the phosphorylation. The Ca2+-dependent actin-binding phosphorylatable protein named Cap 42 (a + b), consisting of two distinct 42,000-Da peptides a and b, was purified to near homogeneity. Peptide b was identified as the phosphorylatable subunit. Substoichiometric amounts of Cap 42 (a + b) reduced the low shear viscosity of F-actin solutions.
Ca2+-dependent actin-binding phosphoprotein in Physarum polycephalum. II. Ca2+-dependent f-actin-capping activity of subunit a and its regulation by phosphorylation of subunit b.
Cap 42 (a + b), a Ca2+-dependent, actin-binding and phosphorylatable protein consisting of two distinct subunits a and b of 42,000 Da in Physarum polycephalum, has been identified as a new F-actin-capping protein. It capped or bound to the fast growing ends of actin filaments and blocked actin polymerization at this end. The capping activity residing in subunit a and its Ca2+-dependency were regulated by phosphorylation of subunit b; subunit a required Ca2+ for its capping activity when subunit b was phosphorylated, whereas this activity became Ca2+ independent when subunit b was dephosphorylated. Subunit b contained at least two phosphorylatable threonine residues and probably three additional phosphorylation sites. Like cytochalasins and other F-actin-capping proteins, Cap 42 (a + b) was able to induce a rapid depolymerization of actin filaments at the slow growing end, and also to nucleate actin polymerization. However, unlike Physarum fragmin, Cap 42 (a + b) had no severing activity leading to the fragmentation of actin filaments. Our results indicate that Cap 42 (a + b) is the first Ca2+-dependent F-actin-capping phosphoprotein whose phosphorylation regulates its actin-binding and vice versa. A possible mechanism of the capping action of Cap 42 (a + b) in vitro and also its conceivable role in the regulation of the Ca2+/actin-dependent cytoplasmic streaming in plasmodia are discussed.
Confirmation of direct angiotensin formation by kallikrein.
This study was undertaken to confirm our previous preliminary observation that hog pancreas kallikrein (EC 3.4.21.35) directly liberated an angiotensin-like substance from human plasma protein Cohn fraction IV-4 at an acidic pH of 4.0-5.0. First, the possibility of proangiotensin or des-Asp1-angiotensin being the pressor substance was ruled out by t.l.c. Secondly, the pressor substance was purified by Sephadex G-25 and Bio-Gel P-2 gel filtration, and finally by high-performance liquid chromatography. The amino acid composition of the isolated pressor substance (residues/mol) was: Asp, 1.03; Val, 1.03; Ile, 1.00; Tyr, 0.69; Phe, 1.04; His, 0.91; Arg, 0.86; Pro, 0.86. This composition was identical with that of angiotensin. Since the reaction mixture was not contaminated with common proteolytic enzymes, such as trypsin, chymotrypsin, renin, cathepsin D and proangiotensin-converting enzyme, and other enzymes activated by kallikrein, it is clear that hog kallikrein directly produces angiotensin in vitro.
[Effects of castration on the gonadotropin level in prepubertal males--a study on pubertal development].
The effects of prepubertal castration on circulating levels of LH and FSH were examined longitudinally in 3 male pseudohermaphrodites (1 yr., 6 yrs., 9 yrs.) and one Lt. monorchid (7 yrs.), and gonadotropin levels of prepubertal anorchism (9 yrs.) were also studied longitudinally. After castration, plasma LH and FSH concentration in the patient 1 yr. of age elevated significantly and progressively, but in two other patients 6 and 7 yrs. of age, a significant elevation of plasma LH and FSH was not observed from 90 to 450 days after the castration. Plasma LH and FSH concentration of one patient 9 yrs. of age, castrated at 1 yr., showed prepubertal values from 9 to 11 yrs. of age, and the abrupt elevation of LH and FSH occurred at 11-2/12 yrs. of age. From these observations we concluded that although castration in early childhood resulted in an immediate elevation of gonadotropin levels, a significant elevation of gonadotropin did not occur in midchildhood castration. These findings have also confirmed the evidence that the hypothalamic-pituitary-gonadal negative feedback mechanism is operative in early childhood, and supported the action of a CNS inhibitory mechanism which restrains the gonadotropin synthesis and secretion and inhibits puberty during the interval of mid-childhood.
Myosin heavy chain kinase inactivated by Ca2+/calmodulin from aggregating cells of Dictyostelium discoideum.
Soluble myosin heavy chain kinases (MHC kinases) were partially purified from growth phase and aggregation-competent cells of Dictyostelium discoideum. In the aggregation-competent cells, two MHC kinases were distinguishable. One of these enzymes, called MHC kinase II, was inactivated by Ca2+ and calmodulin in a highly temperature-dependent reaction. A MHC kinase found in growth phase cells did not have these regulatory properties. Substrate specificities were analysed for MHC kinase II and for the MHC kinase from growth phase cells. Both enzymes phosphorylated threonine residues of the myosin heavy chains of D. discoideum and Physarum polycephalum. Phosphopeptide mapping of D. discoideum myosin and determination of the stoichiometry of its phosphorylation suggested the presence of two phosphorylation sites per heavy chain. Both sites were contained within a 38-kd chymotryptic fragment. The inactivation of MHC kinase II by Ca2+ plus calmodulin suggests this enzyme has a role in the regulation of myosin functions during the chemotactic response of a cell. The phosphorylated myosin had about one third the actin-activated Mg2+-ATPase activity of the non-phosphorylated myosin. Previous findings indicated that stimulation of D. discoideum cells with the chemo-attractant cAMP increases the cytoplasmic Ca2+ concentration. Under these conditions MHC kinase II might be inhibited and the dephosphorylated, more active form of myosin would accumulate.
[Testicular dysfunction with hyperprolactinemia].
Explore the source record for details and available documents.
Electron microscopic mapping of monoclonal antibodies on the tail region of Dictyostelium myosin.
The binding sites of five monoclonal antibodies against myosin of Dictyostelium discoideum have been mapped. These antibodies bind to the tail region of the myosin molecule. By rotary shadowing, images of myosin-antibody complexes were obtained in which the mean distance of the midpoint of an antibody molecule from the myosin heads was localized with a precision better than 2 nm (90% confidence limit). Other quantitative data extracted from electron micrographs provided information on the stoichiometry of antibody-myosin interaction. Certain antibodies interacted with myosin molecules only at a ratio of 1:1. Other antibodies formed complexes of two molecules bound to homologous sites on a double-stranded myosin tail. Affinities were estimated and the abilities of different antibodies to cross-connect two myosin molecules were evaluated.
Myosins from Acanthamoeba castellanii.
Explore the source record for details and available documents.
[Clinical study on the prolactin in male. Report 2. Prolactin levels following castration and exogenous estrogen and androgen administration].
Explore the source record for details and available documents.
[Biochemistry of the renin substrate].
Explore the source record for details and available documents.
[Clinical study on the prolactin in male. Report 1. The secretion of prolactin in the patients with prostatic cancer and hypogonadal men (author's transl)].
Explore the source record for details and available documents.
[Influence of posture and thoracotomy on arterial oxygenation during one-lung anesthesia].
Explore the source record for details and available documents.
[Male hermaphroditism].
Explore the source record for details and available documents.
Proteolytic separation of the actin-activatable ATPase site from the phosphorylation site on the heavy chain of Acanthamoeba myosin IA.
Previous work (Maruta, H., Gadasi, H., Collins, J. H., and Korn, E. D. (1978) J. Biol. Chem. 253, 6292-6300) had shown that phosphorylation of the heavy chain of Acanthamoeba myosin IA is required for actin activation of its Mg2+-ATPase activity and that, like the phosphorylation site, the catalytic site and the actin binding site are also on the heavy chain. We now show that limited digestion of phosphorylated myosin IA by subtilisin allows separation of the catalytically active peptide fragment from the phosphorylated peptide without any significant loss of actin-activated Mg2+-ATPase activity. A proteolytic fragment with full actin-activated Mg2+-ATPase activity has also been isolated from subtilisin digests of nonphosphorylated myosin IA, which, before proteolysis, did not have actin-activated Mg2+-ATPase activity. The simplest interpretation of these data is that, in its nonphosphorylated state, the phosphorylation site of Acanthamoeba myosin IA inhibits the catalytic site and that this inhibition can be reversed either by phosphorylation of the site or by proteolytically separating it from the catalytic site. Alternatively, phosphorylation and proteolysis may, by unrelated mechanisms, induce similar conformational changes in the myosin heavy chain that lead to activation of its actomyosin ATPase activity.
Direct photoaffinity labeling by nucleotides of the apparent catalytic site on the heavy chains of smooth muscle and Acanthamoeba myosins.
The heavy chains of Acanthamoeba myosins. IA, IB and II, turkey gizzard myosin, and rabbit skeletal muscle myosin subfragment-1 were specifically labeled by radioactive ATP, ADP, and UTP, each of which is a substrate or product of myosin ATPase activity, when irradiated with UV light at 0 degrees C. With UTP, as much as 0.45 mol/mol of Acanthamoeba myosin IA heavy chain and 1 mol/mol of turkey gizzard myosin heavy chain was incorporated. Evidence that the ligands were associated with the catalytic site included the observations that reaction occurred only with nucleotides that are substrates or products of the ATPase activity; that the reaction was blocked by pyrophosphate which is an inhibitor of the ATPase activity; that ATP was bound as ADP; and that label was probably restricted to a single peptide following limited subtilisin proteolysis of labeled Acanthamoeba myosin IA heavy chain and extensive cleavage with CNBr and trypsin of labeled turkey gizzard myosin heavy chain.
Ability of kallikrein to generate angiotensin II-like pressor substance and a proposed 'kinin-tensin enzyme system'.
Pig pancreatic kallikrein liberates kallidin from kininogen, whereas trypsin releases bradykinin. Recently, both kallikrein and trypsin have been reported to convert inactive plasma renin to active renin. However, we found that at pH 6.0, trypsin generated an angiotensin II-like pressor substance from human plasma protein in the absence of converting enzyme. This has been isolated and found to have the same amino acid composition as angiotensin II. Thus, in vitro trypsin can directly liberate both the depressor, bradykinin, in weak alkaline conditions, and the pressor, angiotensin II, at weakly acidic pH, from the appropriate substrates. We have now investigated whether kallikrein--a serine protease like trypsin--also generates a pressor substance at weakly acidic pH. Our results demonstrate that it does. We therefore suggest that kallikrein may be involved in a direct link between the pressor and depressor systems and we propose the term 'kinin-tensin system' for this sort of one-enzyme system capable of generating both depressor and pressor substances.