Human cardiac troponin I: precise identification of antigenic epitopes and prediction of secondary structure

Abstract The presence of human cardiac troponin I (hcTnI) in serum is considered to be a highly specific biochemical marker of acute myocardial infarction. To better understand the antigenic properties of hcTnI, a set of 68 overlapping peptides covering the complete amino acid sequence of hcTnI was prepared and used in epitope mapping experiments. All 16 anti-hcTnI monoclonal antibodies tested were found to recognize a peptide epitope, indicating that recognition by anti-hcTnI monoclonal antibodies was not dependent on the tertiary structure of the protein. Furthermore, the peptide reactivity with anti-hcTnI polyclonal antibodies indicated that most of the sequence of the protein was antigenic; in particular, the N- and C-terminal extremities were found to be the strongest antigenic regions. By using accurate secondary structure prediction methods, hcTnI was found to be an all-alpha type protein, with five regions predicted as helices. Matching the results of the epitope analysis with the structural prediction led us to the view that hcTnI is not a globular protein but probably adopts an extended conformation, allowing a large part of the amino acid sequence of this molecule to be recognized by the immune system. This improved knowledge of the antigenic and structural properties of hcTnI may help in developing new antibodies and immunoassays for use in diagnosing myocardial infarction.

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The amino acid sequence of rabbit cardiac troponin I

Biochemical Journal ◽

10.1042/bj1590633 ◽

1976 ◽

Vol 159 (3) ◽

pp. 633-641 ◽

Cited By ~ 59

Author(s):

R J A. Grand ◽

J M Wilkinson ◽

L E More

Keyword(s):

Skeletal Muscle ◽

Amino Acid ◽

Amino Acid Sequence ◽

Inhibitory Activity ◽

Cardiac Troponin ◽

Troponin I ◽

Muscle Protein ◽

Cardiac Troponin I ◽

Skeletal Muscle Protein ◽

Fast Skeletal Muscle

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.

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Amino acid sequence of bovine cardiac troponin I

Biochemistry ◽

10.1021/bi00408a024 ◽

1988 ◽

Vol 27 (8) ◽

pp. 2821-2827 ◽

Cited By ~ 57

Author(s):

John Leszyk ◽

Ranjana Dumaswala ◽

James D. Potter ◽

John H. Collins

Keyword(s):

Amino Acid ◽

Amino Acid Sequence ◽

Cardiac Troponin ◽

Troponin I ◽

Cardiac Troponin I

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Development of Monoclonal Antibodies for an Assay of Cardiac Troponin-I and Preliminary Results in Suspected Cases of Myocardial Infarction

Clinical Chemistry ◽

10.1093/clinchem/38.11.2203 ◽

1992 ◽

Vol 38 (11) ◽

pp. 2203-2214 ◽

Cited By ~ 257

Author(s):

G S Bodor ◽

S Porter ◽

Y Landt ◽

J H Ladenson

Keyword(s):

Myocardial Infarction ◽

Monoclonal Antibodies ◽

Cardiac Troponin ◽

Time Course ◽

Troponin I ◽

Cross Reactivity ◽

Cardiac Troponin I ◽

Sufficient Information ◽

Creatine Kinase Mb ◽

Human Sera

Abstract To improve the specificity of biochemical markers of myocardial infarction (MI), we have developed a double monoclonal "sandwich" enzyme immunoassay to measure cardiac troponin-I (cTnI) in serum. We produced eight IgG monoclonal antibodies against human cardiac troponin-I (cTnI) and tested them against human and animal (canine, bovine, and rabbit) troponins. Five antibodies were cardiac-specific; none of the antibodies were species-specific. Two of the five cTnI-specific monoclonal antibodies were utilized in an immunoassay. Standards were made by adding purified human cTnI to affinity-stripped cTnI-free human sera to cover the range 0-100 micrograms/L for cTnI. The dose-response curve was nonlinear but reproducible. Total assay imprecision (CV) varied between 11% and 21%. The upper limit of the reference range (nonparametric 95% interval) was established as 3.1 micrograms/L by measuring cTnI concentration in sera of 159 hospitalized patients without evidence of cardiac disease. Purified human skeletal TnI up to 10,000 micrograms/L did not affect the assay (calculated cross-reactivity < 0.1%). Diagnostic sensitivities of creatine kinase MB isoenzyme (CK-MB) and cTnI were evaluated retrospectively in 49 consecutive patients with proven MI. In the 30 patients for whom sufficient information was available to establish an accurate time course, CK-MB was more sensitive during the first 4 h after the onset of chest pain, but thereafter the sensitivities were similar up to 48 h. However, cTnI is more cardiac-specific than is CK-MB and remains increased longer than does CK-MB.

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The amino acid sequence of rabbit cardiac troponin I

Biochemical Journal ◽

10.1042/bj1670513e ◽

1977 ◽

Vol 167 (3) ◽

pp. 513.b1-513.b1

Keyword(s):

Amino Acid ◽

Amino Acid Sequence ◽

Cardiac Troponin ◽

Troponin I ◽

Cardiac Troponin I

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Role of Cardiac Troponin I Level in Predicting in Hospital Outcomes in Patients with ST-segment Elevation Myocardial Infarction in Erbil-Iraq

Diyala Journal of Medicine ◽

10.26505/djm.13013150123 ◽

2017 ◽

Vol 13 (1) ◽

pp. 1-7

Author(s):

Salam Naser Zangana ◽

◽

Abdul kareem A AL-Othman ◽

Namir G AL-Tawil ◽

Keyword(s):

Myocardial Infarction ◽

Cardiac Troponin ◽

Troponin I ◽

Cardiac Troponin I ◽

Hospital Outcomes ◽

St Segment Elevation ◽

Segment Elevation Myocardial Infarction ◽

St Segment

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Faculty Opinions recommendation of One-hour rule-in and rule-out of acute myocardial infarction using high-sensitivity cardiac troponin I.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.725420089.793507697 ◽

2015 ◽

Author(s):

Patrick Ray

Keyword(s):

Myocardial Infarction ◽

Acute Myocardial Infarction ◽

Cardiac Troponin ◽

Troponin I ◽

High Sensitivity ◽

Cardiac Troponin I ◽

Rule Out

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Diagnostic Application of Postmortem Cardiac Troponin I Pericardial Fluid/Serum Ratio in Sudden Cardiac Death

Diagnostics ◽

10.3390/diagnostics11040614 ◽

2021 ◽

Vol 11 (4) ◽

pp. 614

Author(s):

Diana Hernández-Romero ◽

María del Rocío Valverde-Vázquez ◽

Juan Pedro Hernández del Rincón ◽

José A. Noguera-Velasco ◽

María D. Pérez-Cárceles ◽

...

Keyword(s):

Myocardial Infarction ◽

Sudden Cardiac Death ◽

Cardiac Troponin ◽

Cardiac Death ◽

Troponin I ◽

Sampling Site ◽

Pericardial Fluid ◽

Cardiac Troponin I ◽

Control Group ◽

Complementary Method

In approximately 5% of unexpected deaths, establishing a conclusive diagnosis exclusively on the basis of anatomo-pathological findings in a classic autopsy is difficult. Postmortem biomarkers have been actively investigated as complementary indicators to help to reach valid conclusions about the circumstances of death. Several studies propose either the pericardial fluid or peripheral veins as a location for troponin determination, but the optimum sampling site is still a matter of debate. Our objective was to evaluate the association between the ratio of troponin values in the pericardial fluid and serum (determined postmortem) and the diagnosis of acute myocardial infarction (AMI) in the context of sudden cardiac death. We included 175 forensic cases. Two groups were established: AMI deaths (48; 27.4%) and the control group (127; 72.6%). The cardiac Troponin I (cTnI) values in the pericardial fluid and the troponin ratio were found to be associated with the cause of death. Univariate regression analyses showed that both age and the cTnI ratio were significantly associated with the diagnosis of AMI death. In a multivariate analysis, adjusting for confounding factors, the age and cTnI ratio were independent predictors of death from myocardial infarction. We performed a receiver operating characteristic (ROC) curve for the cTnI ratio for AMI death and selected a cut-off point. Our biomarker was found to be a valuable and highly effective tool for use in the forensic field as a complementary method to facilitate diagnosis in nonconclusive autopsies.

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Prussian blue-doped PAMAM dendrimer nanospheres for electrochemical immunoassay of human plasma cardiac troponin I without enzymatic amplification

New Journal of Chemistry ◽

10.1039/d1nj01506k ◽

2021 ◽

Author(s):

Fangfang Ma ◽

Gaoshun Ge ◽

Yizhen Fang ◽

Erru Ni ◽

Yuanyuan Su ◽

...

Keyword(s):

Myocardial Infarction ◽

Cardiac Troponin ◽

Troponin I ◽

Biological Fluids ◽

Pamam Dendrimer ◽

Cardiac Troponin I ◽

Electrochemical Immunoassay ◽

Accurate Identification ◽

Enzymatic Amplification ◽

Electrochemical Immunosensing

Rapid and accurate identification of cardiac troponin I (cTnl) in biological fluids is very essential for judging acute myocardial infarction (AMI). Herein, we constructed an enzyme-free electrochemical immunosensing system for...

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Abstract 2425: Absence of Auto-Antibodies against Cardiac Troponin I Predicts Improvement of Left Ventricular Function after Acute Myocardial Infarction

Circulation ◽

10.1161/circ.118.suppl_18.s_724-b ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Florian Leuschner ◽

Jin Li ◽

Stefan Göser ◽

Lars Reinhardt ◽

Renate Öttl ◽

...

Keyword(s):

Myocardial Infarction ◽

Acute Myocardial Infarction ◽

Stroke Volume ◽

Antibody Titer ◽

Cardiac Troponin ◽

Troponin I ◽

Cardiac Troponin I ◽

Igg Antibody ◽

Follow Up Study

Application of antibodies against cardiac troponin I (cTnI-Ab) can induce dilation and dysfunction of the heart in mice. Recently, we demonstrated that immunization with cTnI induces inflammation and fibrosis in myocardium of mice. Others have shown that autoanti-bodies to cTnI are present in patients with acute coronary syndrome. But little is known about the clinical relevance of detected cTnI-Ab. First, anti-cTnI and anti-cTnT antibody titers were measured in sera from 272 patients with dilated- (DCM) and 185 with ischemic- (ICM) cardiomyopathy. Secondly, 108 patients with acute myocardial infarction (AMI) were included for a follow-up study. Heart characteristics were determined by magnetic resonance imaging 4 days and 6 –9 months after AMI. Altogether, in 7,0% of patients with DCM and in 9,2% with ICM an anti-cTnI IgG antibody titer ≥1:160 was measured. In contrast, only in 1,7% of patients with DCM and in 0,5% with ICM an anti-cTnT IgG antibody titer ≥1:160 was detected. Ten out of 108 patients included in the follow-up study were tested positive for cTnI-Ab with IgG Ab titers ≥1:160. TnI-Ab negative patients showed a significant increase in LVEF and stroke volume 6 –9 months after AMI. In contrast, there was no significant increase in LVEF and stroke volume in TnI-Ab positive patients. We demonstrate for the first time that the prevalence of cTnI-Abs in patients with AMI has an impact on the improvement of the LVEF over a study period of 6 –9 months.

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