The amino acid sequence of troponin I from rabbit skeletal muscle.
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ABSTRACT:
SUBMITTER: Wilkinson JM
PROVIDER: S-EPMC1165646 | biostudies-other | 1975 Aug
REPOSITORIES: biostudies-other
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Project description:Troponin I was isolated from six red muscles in the hind leg of the rabbit. Soleus, semi-tendinosus, vastus intermedius and adductor longus muscles contained primarily slow-muscle troponin I, vastus lateralis contained fast-muscle troponin I and quadratus femoris contained a mixture of the two. The complete amino acid sequence of the troponin I from slow muscle was determined. Seven CNBr fragments were isolated and sequenced by using the dansyl-Edman technique after digestion with proteolytic enzymes. The CNBr fragments were ordered by isolation of tryptic peptides containing carboxy[(14)C]methyl-methionine. Direct evidence for the conjunction of residues 8 and 9 has not been obtained, and one of the carboxyl groups between residues 71 and 79 may carry an amide group. Slow-muscle troponin I is a single polypeptide chain of 184 residues with a mol.wt. of 21146. It has a net overall positive charge of 18 at pH7, and an absorption coefficient, A(1%,1cm) (280), of 5.43. The protein was isolated with both a blocked and an unblocked N-terminus, although the nature of the blocking group was not determined. Proline was found to be the N-terminal amino acid. Two forms of the protein could also be distinguished by the presence of an extra two residues at the C-terminus. Comparison of sequences of troponin I from rabbit slow, fast and cardiac muscle shows that homology is most marked in the C-terminal half of the molecules. Towards the N-terminus the homology becomes much less marked. Detailed evidence on which the sequence is based has been deposited as Supplementary Publication SUP 50079 (32 pages) at the British Library (Lending Division), Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies may be obtained in the terms given in Biochem. J. (1977), 161, 1.
| S-EPMC1183635 | biostudies-other
Project description:The complete amino acid sequence of troponin I from rabbit cardiac muscle was determined by the isolation of four unique CNBr fragments, together with overlapping tryptic peptides containing radioactive methionine residues. Overlap data for residues 35-36, 93-94 and 140-145 are incomplete, the sequence at these positions being based on homology with the sequence of the fast-skeletal-muscle protein. Cardiac troponin I is a single polypeptide chain of 206 residues with mol.wt. 23550 and an extinction coefficient, E 1%,1cm/280, of 4.37. The protein has a net positive charge of 14 and is thus somewhat more basic than troponin I from fast-skeletal muscle. Comparison of the sequences of troponin I from cardiac and fast skeletal muscle show that the cardiac protein has 26 extra residues at the N-terminus which account for the larger size of the protein. In the remainder of sequence there is a considerable degree of homology, this being greater in the C-terminal two-thirds of the molecule. The region in the cardiac protein corresponding to the peptide with inhibitory activity from the fast-skeletal-muscle protein is very similar and it seems unlikely that this is the cause of the difference in inhibitory activity between the two proteins. The region responsible for binding troponin C, however, possesses a lower degree of homology. Detailed evidence on which the sequence is based has been deposited as Supplementary Publication SUP 50072 (20 pages), at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7QB, U.K., from whom copies may be obtained on the terms given in Biochem. J. (1976) 153, 5.
| S-EPMC1164163 | biostudies-other
Project description:The amino acid sequence of rabbit muscle triose phosphate isomerase was deduced by characterizing peptides that overlap the tryptic peptides. Thiol groups were modified by oxidation, carboxymethylation or aminoen. About 50 peptides that provided information about overlaps were isolated; the peptides were mostly characterized by their compositions and N-terminal residues. The peptide chains contain 248 amino acid residues, and no evidence for dissimilarity of the two subunits that comprise the native enzyme was found. The sequence of the rabbit muscle enzyme may be compared with that of the coelacanth enzyme (Kolb et al., 1974): 84% of the residues are in identical positions. Similarly, comparison of the sequence with that inferred for the chicken enzyme (Furth et al., 1974) shows that 87% of the residues are in identical positions. Limited though these comparisons are, they suggest that triose phosphate isomerase has one of the lowest rates of evolutionary change. An extended version of the present paper has been deposited as Supplementary Publication SUP 50040 (42 pages) at the British Library (Lending Division) (formerly the National Lending Library for Science and Technology), Boston Spa, Yorks. LS23 7BQ, U.K., from whom copies can be obtained on the terms given in Biochem. J. (1975) 145, 5.
| S-EPMC1165222 | biostudies-other
Project description:The complete amino acid sequence of chicken skeletal-muscle enolase, comprising 433 residues, was determined. The sequence was deduced by automated sequencing of hydroxylamine-cleavage, CNBr-cleavage, o-iodosobenzoic acid-cleavage, clostripain-digest and staphylococcal-proteinase-digest fragments. The presence of several acid-labile peptide bonds and the tenacious aggregation of most CNBr-cleavage fragments meant that a commonly used sequencing strategy involving initial CNBr cleavage was unproductive. Cleavage at the single Asn-Gly peptide bond with hydroxylamine proved to be particularly useful. Comparison of the sequence of chicken enolase with the two yeast enolase isoenzyme sequences shows that the enzyme is strongly conserved, with 60% of the residues identical. The histidine and arginine residues implicated as being important for the activity of yeast enolase are conserved in the chicken enzyme. Secondary-structure predictions are analysed in an accompanying paper [Sawyer, Fothergill-Gilmore & Russell (1986) Biochem. J. 236, 127-130].
| S-EPMC1146794 | biostudies-other
Project description:A method for isolation of troponin T kinase (ATP-protein phosphotransferase, EC 2.7.1.37) from rabbit skeletal muscles in proposed. The method gives a 7000-10 000-fold purification and results in an enzyme with specific activity of 400-800-nmol x min-1 x mg-1 of protein. The molecular weight of tropin T kinase as determined by gel filtration exceeds 500 000. Electrophoresis in polyacrylamide gel in the presence of sodium dodecyl sulphate revealed that isolated preparations of the enzyme consisted of at least three distinct proteins with apparent mol.wt. of 50 000, 46 000 and 31 000. The enzyme phosphorylates isolated troponin T at a rate which exceeds the phosphorylation rates of casein, phosvitin, histones, phosphorylase b and protamine 5-30-fold. Within the whole troponin complex, only troponin T is phosphorylated by the enzyme. The enzyme phosphorylates only the N-terminal serine residue of troponin T, i.e. the site that is normally phosphorylated in the whole troponin complex isolated from rabbit skeletal muscles.
| S-EPMC1161992 | biostudies-other
Project description:The complete amino acid sequence of human skeletal-muscle fructose-bisphosphate aldolase, comprising 363 residues, was determined. The sequence was deduced by automated sequencing of CNBr-cleavage, o-iodosobenzoic acid-cleavage, trypsin-digest and staphylococcal-proteinase-digest fragments. Comparison of the sequence with other class I aldolase sequences shows that the mammalian muscle isoenzyme is one of the most highly conserved enzymes known, with only about 2% of the residues changing per 100 million years. Non-mammalian aldolases appear to be evolving at the same rate as other glycolytic enzymes, with about 4% of the residues changing per 100 million years. Secondary-structure predictions are analysed in an accompanying paper [Sawyer, Fothergill-Gilmore & Freemont (1988) Biochem. J. 249, 789-793].
| S-EPMC1148774 | biostudies-other
Project description:Essential amino acids (EAA) stimulate skeletal muscle mammalian target of rapamycin complex 1 (mTORC1) signaling and protein synthesis. It has recently been reported that an increase in amino acid (AA) transporter expression during anabolic conditions is rapamycin-sensitive. The purpose of this study was to determine whether an increase in EAA availability increases AA transporter expression in human skeletal muscle. Muscle biopsies were obtained from the vastus lateralis of seven young adult subjects (3 male, 4 female) before and 1-3 h after EAA ingestion (10 g). Blood and muscle samples were analyzed for leucine kinetics using stable isotopic techniques. Quantitative RT-PCR, and immunoblotting were used to determine the mRNA and protein expression, respectively, of AA transporters and members of the general AA control pathway [general control nonrepressed (GCN2), activating transcription factor (ATF4), and eukaryotic initiation factor (eIF2) alpha-subunit (Ser(52))]. EAA ingestion increased blood leucine concentration, delivery of leucine to muscle, transport of leucine from blood into muscle, intracellular muscle leucine concentration, ribosomal protein S6 (Ser(240/244)) phosphorylation, and muscle protein synthesis. This was followed with increased L-type AA transporter (LAT1), CD98, sodium-coupled neutral AA transporter (SNAT2), and proton-coupled amino acid transporter (PAT1) mRNA expression at 1 h (P < 0.05) and modest increases in LAT1 protein expression (3 h post-EAA) and SNAT2 protein expression (2 and 3 h post-EAA, P < 0.05). Although there were no changes in GCN2 expression and eIF2 alpha phosphorylation, ATF4 protein expression reached significance by 2 h post-EAA (P < 0.05). We conclude that an increase in EAA availability upregulates human skeletal muscle AA transporter expression, perhaps in an mTORC1-dependent manner, which may be an adaptive response necessary for improved AA intracellular delivery.
| S-EPMC2867366 | biostudies-literature
Project description:1. The p.m.r. spectra of the larger CNBr-cleavage peptides of troponin I from rabbit fast-twitch skeletal muscle corresponded largely to those of fairly flexible solution structures. 2. On addition of troponin C to each of the CNBr-cleavage peptides in turn, perturbations of side chains were noted only for peptides CN5 (residues 1-21) and CN4 (residues 96-116). 3. In the presence of Ca2+, troponin C induced perturbations of the side chains of threonine-11, alanine, isoleucine and arginine residues of peptide CN5. 4. In the presence of Ca2+, troponin C induced perturbations of the side chains of phenylalanine, lysine and leucine residues of peptide CN4. 5. Irrespective of the presence or absence of Ca2+, specific interaction with actin was observed only with peptide CN4. In this case the side chains of arginine residues were perturbed. 6. It is concluded that actin interacts with the C-terminal region of peptide CN4, whereas troponin C interacts with the N-terminal region of peptide CN4 and with peptide CN5.
| S-EPMC1158193 | biostudies-other
Project description:Time-resolved changes in the conformation of troponin in the thin filaments of skeletal muscle were followed during activation in situ by photolysis of caged calcium using bifunctional fluorescent probes in the regulatory and the coiled-coil (IT arm) domains of troponin. Three sequential steps in the activation mechanism were identified. The fastest step (1,100 s(-1)) matches the rate of Ca(2+) binding to the regulatory domain but also dominates the motion of the IT arm. The second step (120 s(-1)) coincides with the azimuthal motion of tropomyosin around the thin filament. The third step (15 s(-1)) was shown by three independent approaches to track myosin head binding to the thin filament, but is absent in the regulatory head. The results lead to a four-state structural kinetic model that describes the molecular mechanism of muscle activation in the thin filament-myosin head complex under physiological conditions.
| S-EPMC3970506 | biostudies-literature
Project description:BackgroundMuscle weakness is a common symptom in numerous diseases and a regularly occurring problem associated with ageing. Prolonged low-frequency force depression (PLFFD) is a form of exercise-induced skeletal muscle weakness observed after exercise. Three different intramuscular mechanisms underlying PLFFD have been identified: decreased sarcoplasmic reticulum Ca2+ release, decreased myofibrillar Ca2+ sensitivity, and myofibrillar dysfunction. We here used these three forms of PLFFD as models to study the effectiveness of a fast skeletal muscle troponin activator, CK-2066260, to mitigate muscle weakness.MethodsExperiments were performed on intact single muscle fibres or fibre bundles from mouse flexor digitorum brevis, which were stimulated with electrical current pulses, while force and the free cytosolic [Ca2+ ] ([Ca2+ ]i ) were measured. PLFFD was induced by three different stimulation protocols: (i) repeated isometric contractions at low intensity (350 ms tetani given every 5 s for 100 contractions); (ii) repeated isometric contractions at high intensity (250 ms tetani given every 0.5 s for 300 contractions); and (iii) repeated eccentric contractions (350 ms tetani with 20% length increase given every 20 s for 10 contractions). The extent and cause of PLFFD were assessed by comparing the force-[Ca2+ ]i relationship at low (30 Hz) and high (120 Hz) stimulation frequencies before (control) and 30 min after induction of PLFFD, and after an additional 5 min of rest in the presence of CK-2066260 (10 μM).ResultsProlonged low-frequency force depression following low-intensity and high-intensity fatiguing contractions was predominantly due to decreased sarcoplasmic reticulum Ca2+ release and decreased myofibrillar Ca2+ sensitivity, respectively. CK-2066260 exposure resulted in marked increases in 30 Hz force from 52 ± 16% to 151 ± 13% and from 6 ± 4% to 98 ± 40% of controls with low-intensity and high-intensity contractions, respectively. Following repeated eccentric contractions, PLFFD was mainly due to myofibrillar dysfunction, and it was not fully reversed by CK-2066260 with 30 Hz force increasing from 48 ± 8% to 76 ± 6% of the control.ConclusionsThe fast skeletal muscle troponin activator CK-2066260 effectively mitigates muscle weakness, especially when it is caused by impaired activation of the myofibrillar contractile machinery due to either decreased sarcoplasmic reticulum Ca2+ release or reduced myofibrillar Ca2+ sensitivity.
| S-EPMC7749611 | biostudies-literature