Deciphering modifications in swine cardiac troponin I by top-down high-resolution tandem mass spectrometry |
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Authors: | Jiang Zhang Xintong Dong Timothy A Hacker Ying Ge |
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Institution: | (1) Department of Physiology, University of Wisconsin-Madison, Madison, WI 53706, USA;(2) Human Proteomics Program, University of Wisconsin-Madison, Madison, WI 53706, USA;(3) Department of Physiology, University of Arizona, Tucson, AZ 85724, USA;(4) Molecular Cardiovascular Research Program, Arizona Diabetes Program, MRB 411, University of Arizona College of Medicine, 1656 E Mabel Ave., Tucson, AZ 85724, USA; |
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Abstract: | Cardiac troponin I (cTnI) is an important regulatory protein in cardiac muscle, and its modification represents a key mechanism
in the regulation of cardiac muscle contraction and relaxation. cTnI is often referred to as the “gold-standard” serum biomarker
for diagnosing patients with acute cardiac injury since it is unique to the heart and released into the circulation following
necrotic death of cardiac tissue. The swine (Sus scrofa) heart model is extremely valuable for cardiovascular research since the heart anatomy and coronary artery distribution of
swine are almost identical to those of humans. Herein, we report a comprehensive characterization of the modifications in
swine cTnI using top-down high-resolution tandem mass spectrometry in conjugation with immunoaffinity chromatography purification.
High-resolution high accuracy mass spectrometry revealed that swine cTnI affinity purified from domestic pig hearts was N-terminally
acetylated and phosphorylated. Electron capture disassociation is uniquely suited for localization of labile phosphorylations,
which unambiguously identified Ser22/Ser23 as the only basally phosphorylated sites that are well-known to be regulated by
protein kinase A and protein kinase C. Moreover, a combination of tandem mass spectrometry with sequence homology alignment
effectively localized a single amino acid polymorphism, V116A, representing a novel genetic variant of swine cTnI. Overall,
our studies demonstrated the unique power of top-down high-resolution tandem mass spectrometry in the characterization of
protein modifications, including labile phosphorylation and unexpected sequence variants. |
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