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Structural stabilization of protein 4.1R FERM domain upon binding to apo-calmodulin: novel insights into the biological significance of the calcium-independent binding of calmodulin to protein 4.1R.
| Content Provider | Semantic Scholar |
|---|---|
| Author | Nunomura, Wataru Sasakura, Daisuke Shiba, Kohei Nakamura, Shigeyoshi Kidokoro, Shun-Ichi Takakuwa, Yuichi |
| Copyright Year | 2011 |
| Abstract | In erythrocytes, 4.1R80 (80 kDa isoform of protein 4.1R) binds to the cytoplasmic tail of the transmembrane proteins band 3 and GPC (glycophorin C), and to the membrane-associated protein p55 through the N- (N-terminal), α- (α-helix-rich) and C- (C-terminal) lobes of R30 [N-terminal 30 kDa FERM (4.1/ezrin/radixin/moesin) domain of protein 4.1R] respectively. We have shown previously that R30 binds to CaM (calmodulin) in a Ca2+-independent manner, the equilibrium dissociation constant (Kd) for R30-CaM binding being very similar (in the submicromolar range) in the presence or absence of Ca2+. In the present study, we investigated the consequences of CaM binding on R30's structural stability using resonant mirror detection and FTIR (Fourier-transform IR) spectroscopy. After a 30 min incubation above 40° C, R30 could no longer bind to band 3 or to GPC. In contrast, R30 binding to p55, which could be detected at a temperature as low as 34° C, was maintained up to 44° C in the presence of apo-CaM. Dynamic light scattering measurements indicated that R30, either alone or complexed with apo-CaM, did not aggregate up to 40° C. FTIR spectroscopy revealed that the dramatic variations in the structure of the β-sheet structure of R30 observed at various temperatures were minimized in the presence of apo-CaM. On the basis of Kd values calculated at various temperatures, ΔCp and ΔG° for R30 binding to apo-CaM were determined as -10 kJ · K(-1) · mol-1 and ~ -38 kJ · mol(-1) at 37° C (310.15 K) respectively. These data support the notion that apo-CaM stabilizes R30 through interaction with its β-strand-rich C-lobe and provide a novel function for CaM, i.e. structural stabilization of 4.1R80. |
| File Format | PDF HTM / HTML |
| DOI | 10.1042/BJ20110676 |
| PubMed reference number | 21848512 |
| Journal | Medline |
| Volume Number | 440 |
| Issue Number | 3 |
| Alternate Webpage(s) | http://www.biochemj.org/content/ppbiochemj/440/3/367.full.pdf |
| Alternate Webpage(s) | https://doi.org/10.1042/BJ20110676 |
| Journal | The Biochemical journal |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
