TY - JOUR
T1 - Correlation of fluorescence and circular dichroism spectroscopy with electrospray ionization mass spectrometry in the determination of tertiary conformational changes in calcium-binding proteins
AU - Veenstra, Timothy D.
AU - Johnson, Kenneth L.
AU - Tomlinson, Andy J.
AU - Kumar, Rajiv
AU - Naylor, Stephen
PY - 1998
Y1 - 1998
N2 - We compared changes in the fluorescence, circular dichroism (CD) and multiply charged electrospray ionization mass spectrometry (ESI-MS) spectra of three calcium (Ca2+)-binding proteins upon the binding of Ca+. The proteins used were rat brain calbindin D(28K) and two deletion mutants, one lacking EF-hand 2 (calbindin Δ2) and the other lacking EF-hands 2 and 6 (calbindin Δ2,6). Large changes in the intrinsic protein fluorescence spectrum were seen upon the addition of Ca2+ to calbindin D(28K) and Δ2, while a less significant change was observed for calbindin Δ2,6. In a fluorescent study in which p-toluidinyl-2-naphthalene-6-sulfonote, a fluorescent probe which binds to hydrophobic surfaces within proteins, was used; calbindin D(28K) and Δ2 again showed a greater change in fluorescence intensity upon Ca2+-binding than calbindin Δ2,6. Near UV-CD studies, which measure changes within the tertiary structure of a protein, showed greater changes in the spectrum of calbindin D(28K) and Δ2 compared to calbindin Δ2,6 upon Ca2+-binding. Far UV-CD studies, which measures changes within the secondary structure of a protein, however, showed that the spectrum of all three proteins underwent only minor changes upon metal-binding. The ESI-MS studies showed that as the proteins were titrated with Ca2+ a gradual shift in the mass envelope from higher to lower charge states occurs. In the case of calbindin D(28K) and calbindin Δ2, however, a complete shift in the mass envelope towards the lower charge states is observed upon saturation with Ca2+, whereas for calbindin Δ2,6, the shift in the charge states is still relatively evenly distributed between high and low charge states. Changes within the ESI-MS spectrum observed upon the addition of Ca2+ correlated with Ca2+-induced changes observed with near-ultraviolet CD, intrinsic fluorescence spectroscopy, and spectroscopy using the fluorescent probe. Changes in the far ultraviolet-CD spectra of the calbindins, however, did not correlate with changes in the ESI-MS spectra upon calcium binding. The results show that ESI-MS can be use to detect changes in the tertiary structure of calcium-binding proteins induced by the binding of metal to the proteins.
AB - We compared changes in the fluorescence, circular dichroism (CD) and multiply charged electrospray ionization mass spectrometry (ESI-MS) spectra of three calcium (Ca2+)-binding proteins upon the binding of Ca+. The proteins used were rat brain calbindin D(28K) and two deletion mutants, one lacking EF-hand 2 (calbindin Δ2) and the other lacking EF-hands 2 and 6 (calbindin Δ2,6). Large changes in the intrinsic protein fluorescence spectrum were seen upon the addition of Ca2+ to calbindin D(28K) and Δ2, while a less significant change was observed for calbindin Δ2,6. In a fluorescent study in which p-toluidinyl-2-naphthalene-6-sulfonote, a fluorescent probe which binds to hydrophobic surfaces within proteins, was used; calbindin D(28K) and Δ2 again showed a greater change in fluorescence intensity upon Ca2+-binding than calbindin Δ2,6. Near UV-CD studies, which measure changes within the tertiary structure of a protein, showed greater changes in the spectrum of calbindin D(28K) and Δ2 compared to calbindin Δ2,6 upon Ca2+-binding. Far UV-CD studies, which measures changes within the secondary structure of a protein, however, showed that the spectrum of all three proteins underwent only minor changes upon metal-binding. The ESI-MS studies showed that as the proteins were titrated with Ca2+ a gradual shift in the mass envelope from higher to lower charge states occurs. In the case of calbindin D(28K) and calbindin Δ2, however, a complete shift in the mass envelope towards the lower charge states is observed upon saturation with Ca2+, whereas for calbindin Δ2,6, the shift in the charge states is still relatively evenly distributed between high and low charge states. Changes within the ESI-MS spectrum observed upon the addition of Ca2+ correlated with Ca2+-induced changes observed with near-ultraviolet CD, intrinsic fluorescence spectroscopy, and spectroscopy using the fluorescent probe. Changes in the far ultraviolet-CD spectra of the calbindins, however, did not correlate with changes in the ESI-MS spectra upon calcium binding. The results show that ESI-MS can be use to detect changes in the tertiary structure of calcium-binding proteins induced by the binding of metal to the proteins.
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U2 - 10.1002/(SICI)1097-0231(19980529)12:10<613::AID-RCM202>3.0.CO;2-5
DO - 10.1002/(SICI)1097-0231(19980529)12:10<613::AID-RCM202>3.0.CO;2-5
M3 - Article
AN - SCOPUS:0031899560
SN - 0951-4198
VL - 12
SP - 613
EP - 619
JO - Rapid Communications in Mass Spectrometry
JF - Rapid Communications in Mass Spectrometry
IS - 10
ER -