Interaction of troponin I and troponin C

Ap, Campbell; Bd, Sykes

doi:10.1016/0022-2836(91)90219-v

Cited by 76 publications

(26 citation statements)

References 73 publications

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“…Available biochemical data support models for interactions of TnIp, corresponding to cTnI residues 129–149, with either both globular domains, the C‐domain, and/or the D/E linker region of TnC [7–9,15–19]. These models suggest exposure of hydrophobic patches on each globular domain of cTnC upon the binding of Ca 2+ and interaction of an amphiphilic α‐helical TnIp with the exposed hydrophobic surface [20]. However, other regions of cTnI have been shown to interact with the globular domains of cTnC.…”

Section: Introductionmentioning

confidence: 76%

Cardiac troponin I inhibitory peptide: location of interaction sites on troponin C

et al. 2000

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Cardiac troponin I(129^149) binds to the calcium saturated cardiac troponin C/troponin I(1^80) complex at two distinct sites. Binding of the first equivalent of troponin I(1291 49) was found to primarily affect amide proton chemical shifts in the regulatory domain, while the second equivalent perturbed amide proton chemical shifts within the D/E linker region. Nitrogen-15 transverse relaxation rates showed that binding the first equivalent of inhibitory peptide to the regulatory domain decreased conformational exchange in defunct calcium binding site I and that addition of the second equivalent of inhibitory peptide decreased flexibility in the D/E linker region. No interactions between the inhibitory peptide and the C-domain of cardiac troponin C were detected by these methods demonstrating that the inhibitory peptide cannot displace cTnI(1^80) from the C-domain.z 2000 Federation of European Biochemical Societies.

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Section: Introductionmentioning

confidence: 76%

Cardiac troponin I inhibitory peptide: location of interaction sites on troponin C

et al. 2000

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“…Tr-NOESY (16) (15,27,28) and Tr-ROESY (29) NMR experiments were performed on the consensus TAGRFGGGQVGPP (sequence 10) peptide to study its molecular conformation when bound to mAb 44.1 and to test conclusions drawn from the phage-display analysis. Tr-NOESY analysis could not be carried out on peptide 9 (ATAGRFGGPQVNPI), which more closely resembled both regions of Cyt b, because under the conditions investigated it was bound too tightly by mAb 44.1.…”

Section: Discussionmentioning

confidence: 99%

Antibody Imprint of a Membrane Protein Surface

Burritt¹,

Busse²,

Gizachew³

et al. 1998

Journal of Biological Chemistry

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Structural features of the integral membrane protein flavocytochrome b (Cyt b) were discovered using an antibody "imprint" of the Cyt b surface. Amino acid sequences were selected from a random nonapeptide phage-display library by their affinity for the monoclonal antibody 44.1 binding site, which recognizes the native conformation of the p22 phox subunit of Cyt b. Transferred nuclear Overhauser effect spectroscopy and rotating frame Overhauser effect spectroscopy NMR were used to study the antibody-bound conformation of a synthetic peptide derived from phage-displayed sequences. The NMR data supported the phagedisplay analysis suggesting the existence of a complex epitope and allowed the modeling of the close spatial proximity of the epitope components 29 TAGRF 33 and 183 PQVNPI 188 from discontinuous regions of p22 phox . Although these regions are separated by two putative membrane-spanning domains and are 150 residues apart in the sequence, they appear to combine to form a complex epitope on the cytosolic surface of the transmembrane protein. NMR constraints, measured from the antibody-bound conformation of a composite peptide mimetic of the Cyt b epitope, and one constraint inferred from the phage-display results, were used to demonstrate the close proximity of these two regions. This information provides a low resolution view of the tertiary structure of the native discontinuous epitope on the Cyt b surface. Given additional antibodies, such imprint analysis has the potential for producing structural constraints to help support molecular modeling of this and other low abundance or noncrystallizable proteins.Human phagocyte flavocytochrome b (Cyt b) 1 is an electron transferase that directs metabolic electrons across the plasma membrane to reduce molecular oxygen and form superoxide (O 2 . ). The production of superoxide by phagocytes, which involves modulation of Cyt b structure, is essential for antimicrobial host defense (1), plays a central role in inflammatory tissue injury (2), and may play a more general role in cellular regulation (3). Individuals with a defective Cyt b have insufficient superoxide production, suffer from chronic granulomatous disease (4), and sustain repeated life-threatening infections (5). Despite its cardinal role in many inflammatory processes and possibly in growth regulation, few experimental methods have been able to provide information on the structure of Cyt b. Therefore, we have developed an alternative method to describe topological features of the Cyt b surface. Because antibodies and their cognate antigens form complementary surfaces of interaction (6), we have sought structural information about Cyt b from an antibody binding site, specific for the Cyt b surface. We recently reported mapping of monoclonal antibody epitopes and functional sites of Cyt b, using random sequence phage-display peptide libraries (7;8). mAb 44.1 recognizes Cyt b in situ in permeabilized human neutrophils and thus contains information about the three-dimensional structure of the protein sur...

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“…Early 1 H NMR study of the skeletal TnI isoform involving transferred NOEs by Campbell and co-workers (33,34) led to the proposal that the inhibitory region, sTnI-(104 -115) (cTnI-(136 -147)), adopts a short helix, distorted around two central proline residues, and this structure was subsequently docked within the hydrophobic cleft on sCTnC (35). The crystal structure of sTnC in complex with the N-terminal regulatory peptide of sTnI-(1-47) (Rp40) presented by Vassylyev et al (21) showed that Rp40 adopts a helical structure and binds in the hydrophobic cleft of sCTnC, and these workers modeled the inhibitory region as adopting a helical conformation away from the hydrophobic cleft.…”

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confidence: 99%

Structure and Dynamics of the C-domain of Human Cardiac Troponin C in Complex with the Inhibitory Region of Human Cardiac Troponin I

Lindhout¹,

Sykes

2003

Journal of Biological Chemistry

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Cardiac troponin C is the Ca 2؉ -dependent switch for heart muscle contraction. Troponin C is associated with various other proteins including troponin I and troponin T. The interaction between the subunits within the troponin complex is of critical importance in understanding contractility. Following a Ca 2؉ signal to begin contraction, the inhibitory region of troponin I comprising residues Thr 128 -Arg 147 relocates from its binding surface on actin to troponin C, triggering movement of troponin-tropomyosin within the thin filament and thereby freeing actin-binding site(s) for interactions with the myosin ATPase of the thick filament to generate the power stroke. The structure of calcium-saturated cardiac troponin C (C-domain) in complex with the inhibitory region of troponin I was determined using multinuclear and multidimensional nuclear magnetic resonance spectroscopy. The structure of this complex reveals that the inhibitory region adopts a helical conformation spanning residues Leu 134 -Lys 139 , with a novel orientation between the E-and H-helices of troponin C, which is largely stabilized by electrostatic interactions. By using isotope labeling, we have studied the dynamics of the protein and peptide in the binary complex. The structure of this inhibited complex provides a framework for understanding into interactions within the troponin complex upon heart contraction.The binding of Ca 2ϩ to the troponin complex initiates cardiac muscle contraction (1-5). The troponin complex is composed of three subunits: troponin C (TnC), 1 troponin I (TnI), and troponin T (TnT) (6). The three subunits of the troponin complex are necessary for Ca 2ϩ -induced regulation of cardiac muscle contractility. TnC, the Ca 2ϩ -sensitive component of the complex, is a member of the EF-hand family of Ca 2ϩ -binding proteins and contains two high affinity Ca 2ϩ /Mg 2ϩ -binding sites (sites III and IV) in the C-terminal domain and one low affinity Ca 2ϩ -binding site (site II) in the N-terminal domain (7-9). At physiological conditions during muscle relaxation, the two C-terminal Ca 2ϩ /Mg 2ϩ -binding sites are occupied, and the N-terminal Ca 2ϩ -binding site is unoccupied. During the onset of muscle contraction, a transient increase in cytosolic Ca 2ϩ concentrations allows the low affinity N-terminal domain to bind Ca 2ϩ , resulting in the initiation of heart contraction (10). TnI is the subunit that in the presence of tropomyosin inhibits myosin Mg 2ϩ -ATPase activity. TnI inhibition is removed by the binding of Ca 2ϩ to the N-terminal domain of the TnC subunit (11). TnT is the subunit that binds tropomyosin, TnC, and TnI, anchoring the troponin complex to the thin filament and aids in the propagation of Ca 2ϩ -induced conformational changes (12, 13).The structure of cardiac TnC, sharing sequence and structural similarities to the skeletal isoform, has been solved by both x-ray crystallography and NMR spectroscopy (7,(15)(16)(17)(18)(19). Upon Ca 2ϩ binding, there is an opening of the N-domain of the skeletal isoform, whereas th...

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Interaction of troponin I and troponin C

Cited by 76 publications

References 73 publications

Cardiac troponin I inhibitory peptide: location of interaction sites on troponin C

Cardiac troponin I inhibitory peptide: location of interaction sites on troponin C

Antibody Imprint of a Membrane Protein Surface

Structure and Dynamics of the C-domain of Human Cardiac Troponin C in Complex with the Inhibitory Region of Human Cardiac Troponin I

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