Rat skin calcium-binding protein is parvalbumin.
Ontology highlight
ABSTRACT:
SUBMITTER: MacManus JP
PROVIDER: S-EPMC1145147 | biostudies-other | 1985 Jul
REPOSITORIES: biostudies-other
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Project description:Strontium salts are used for treatment of osteoporosis and bone cancer, but their impact on calcium-mediated physiological processes remains obscure. To explore Sr2+ interference with Ca2+ binding to proteins of the EF-hand family, we studied Sr2+/Ca2+ interaction with a canonical EF-hand protein, α-parvalbumin (α-PA). Evaluation of the equilibrium metal association constants for the active Ca2+ binding sites of recombinant human α-PA ('CD' and 'EF' sites) from fluorimetric titration experiments and isothermal titration calorimetry data gave 4 × 109 M-1 and 4 × 109 M-1 for Ca2+, and 2 × 107 M-1 and 2 × 106 M-1 for Sr2+. Inactivation of the EF site by homologous substitution of the Ca2+-coordinating Glu in position 12 of the EF-loop by Gln decreased Ca2+/Sr2+ affinity of the protein by an order of magnitude, whereas the analogous inactivation of the CD site induced much deeper suppression of the Ca2+/Sr2+ affinity. These results suggest that Sr2+ and Ca2+ bind to CD/EF sites of α-PA and the Ca2+/Sr2+ binding are sequential processes with the CD site being occupied first. Spectrofluorimetric Sr2+ titration of the Ca2+-loaded α-PA revealed presence of secondary Sr2+ binding site(s) with an apparent equilibrium association constant of 4 × 105 M-1. Fourier-transform infrared spectroscopy data evidence that Ca2+/Sr2+-loaded forms of α-PA exhibit similar states of their COO- groups. Near-UV circular dichroism (CD) data show that Ca2+/Sr2+ binding to α-PA induce similar changes in symmetry of microenvironment of its Phe residues. Far-UV CD experiments reveal that Ca2+/Sr2+ binding are accompanied by nearly identical changes in secondary structure of α-PA. Meanwhile, scanning calorimetry measurements show markedly lower Sr2+-induced increase in stability of tertiary structure of α-PA, compared to the Ca2+-induced effect. Theoretical modeling using Density Functional Theory computations with Polarizable Continuum Model calculations confirms that Ca2+-binding sites of α-PA are well protected against exchange of Ca2+ for Sr2+ regardless of coordination number of Sr2+, solvent exposure or rigidity of sites. The latter appears to be a key determinant of the Ca2+/Sr2+ selectivity. Overall, despite lowered affinity of α-PA to Sr2+, the latter competes with Ca2+ for the same EF-hands and induces similar structural rearrangements. The presence of a secondary Sr2+ binding site(s) could be a factor contributing to Sr2+ impact on the functional activity of proteins.
| S-EPMC8392015 | biostudies-literature
Project description:Molecular dynamics simulations have been used to investigate the relationship between the coordinating residues of the EF-hand calcium binding loop of parvalbumin and the overall plasticity and flexibility of the protein. The first simulation modeled the transition from Ca(2+) to Mg(2+) coordination by varying the van der Waals parameters for the bound metal ions. The glutamate at position 12 could be accurately and reversibly seen to be a source of selective bidentate ligation of Ca(2+) in the simulations. A second simulation correlated well with the experimental observation that an E101D substitution at EF loop position 12 results in a dramatically less tightly bound monodentate Ca(2+) coordination by aspartate. A final set of simulations investigated Ca(2+) binding in the E101D mutant loop in the presence of applied external forces designed to impose bidentate coordination. The results of these simulations illustrate that the aspartate is capable of attaining a suitable orientation for bidentate coordination, thus implying that it is the inherent rigidity of the loop that prevents bidentate coordination in the parvalbumin E101D mutant.
| S-EPMC1301919 | biostudies-other
Project description:BACKGROUND: Apoptosis is a highly ordered and orchestrated multiphase process controlled by the numerous cellular and extra-cellular signals, which executes the programmed cell death via release of cytochrome c alterations in calcium signaling, caspase-dependent limited proteolysis and DNA fragmentation. Besides the general modifiers of apoptosis, several tissue-specific regulators of this process were identified including HAX1 (HS-1 associated protein X-1) - an anti-apoptotic factor active in myeloid cells. Although HAX1 was the subject of various experimental studies, the mechanisms of its action and a functional link connected with the regulation of apoptosis still remains highly speculative. FINDINGS: Here we provide the data which suggests that HAX1 may act as a regulator or as a sensor of calcium. On the basis of iterative similarity searches, we identified a set of distant homologs of HAX1 in insects. The applied fold recognition protocol gives us strong evidence that the distant insects' homologs of HAX1 are novel parvalbumin-like calcium binding proteins. Although the whole three EF-hands fold is not preserved in vertebrate our analysis suggests that there is an existence of a potential single EF-hand calcium binding site in HAX1. The molecular mechanism of its action remains to be identified, but the risen hypothesis easily translates into previously reported lines of various data on the HAX1 biology as well as, provides us a direct link to the regulation of apoptosis. Moreover, we also report that other family of myeloid specific apoptosis regulators - myeloid leukemia factors (MLF1, MLF2) share the homologous C-terminal domain and taxonomic distribution with HAX1. CONCLUSIONS: Performed structural and active sites analyses gave new insights into mechanisms of HAX1 and MLF families in apoptosis process and suggested possible role of HAX1 in calcium-binding, still the analyses require further experimental verification.
| S-EPMC2914655 | biostudies-literature
Project description:?-Lactalbumin (?-LA) is a small (Mr 14,200), acidic (pI 4-5), Ca2+-binding protein. ?-LA is a regulatory component of lactose synthase enzyme system functioning in the lactating mammary gland. The protein possesses a single strong Ca2+-binding site, which can also bind Mg2+, Mn2+, Na+, K+, and some other metal cations. It contains several distinct Zn2+-binding sites. Physical properties of ?-LA strongly depend on the occupation of its metal binding sites by metal ions. In the absence of bound metal ions, ?-LA is in the molten globule-like state. The binding of metal ions, and especially of Ca2+, increases stability of ?-LA against the action of heat, various denaturing agents and proteases, while the binding of Zn2+ to the Ca2+-loaded protein decreases its stability and causes its aggregation. At pH 2, the protein is in the classical molten globule state. ?-LA can associate with membranes at neutral or slightly acidic pH at physiological temperatures. Depending on external conditions, ?-LA can form amyloid fibrils, amorphous aggregates, nanoparticles, and nanotubes. Some of these aggregated states of ?-LA can be used in practical applications such as drug delivery to tissues and organs. ?-LA and some of its fragments possess bactericidal and antiviral activities. Complexes of partially unfolded ?-LA with oleic acid are cytotoxic to various tumor and bacterial cells. ?-LA in the cytotoxic complexes plays a role of a delivery carrier of cytotoxic fatty acid molecules into tumor and bacterial cells across the cell membrane. Perhaps in the future the complexes of ?-LA with oleic acid will be used for development of new anti-cancer drugs.
| S-EPMC7565966 | biostudies-literature
Project description:Mammals express two parvalbumins-an alpha isoform and a beta isoform. In rat, the alpha-parvalbumin (alpha-PV) exhibits superior divalent ion affinity. For example, the standard free energies for Ca2+ binding differ by 5.5 kcal/mol in 0.15 M KCl (pH 7.4). High-resolution structures of the Ca2+-bound proteins provide little insight into this disparity, prompting a structural analysis of the apo-proteins. A recent analysis of rat beta-PV suggested that Ca2+ removal provokes substantial conformational changes-reorientation of the C, D, and E helices; reorganization of the hydrophobic core; reduced interdomain contact; and remodeling of the AB domain. The energetic penalty attendant to reversing these changes, it was suggested, could contribute to the attenuated divalent ion-binding signature of that protein. That hypothesis is supported by data presented herein, describing the solution structure and peptide backbone dynamics of Ca2+-free rat alpha-PV. In marked contrast to rat beta-PV, the apo- and Ca2+-loaded forms of the rat alpha isoform are quite similar. Significant structural differences appear to be confined to the loop regions of the molecule. This finding implies that the alpha-PV isoform enjoys elevated divalent ion affinity because the metal ion-binding events do not require major structural rearrangement and the concomitant sacrifice of binding energy.
| S-EPMC2248305 | biostudies-literature
Project description:Relative to other parvalbumin isoforms, the mammalian beta-parvalbumin (oncomodulin) displays attenuated divalent ion affinity. High-resolution structural data for the Ca(2+)-bound protein have provided little insight into the physical basis for this behavior, prompting an examination of the unliganded state. This article describes the solution structure and peptide backbone dynamics of Ca(2+)-free rat beta-parvalbumin (beta-PV). Ca(2+) removal evidently provokes significant structural alterations. Interaction between the D helix and the AB domain in the Ca(2+)-bound protein is greatly diminished in the apo-form, permitting the D helix to straighten. There is also a significant reorganization of the hydrophobic core and a concomitant remodeling of the interface between the AB and CD-EF domains. These modifications perturb the orientation of the C and D helices, and the energetic penalty associated with their reversal could contribute to the low-affinity signature of the CD site. By contrast, Ca(2+) removal causes a comparatively minor perturbation of the E and F helices, consistent with the more typical divalent ion affinity observed for the EF site. Ca(2+)-free rat beta-PV retains structural rigidity on the picosecond-nanosecond timescale. At 20 degrees C, the majority of amide vectors show no evidence for motion on timescales above 20 ps, and the average order parameter for the entire molecule is 0.92.
| S-EPMC2206965 | biostudies-literature
Project description:PURPOSE: Pterygium is an ocular surface disease of unknown etiology associated with epithelial and fibrovascular outgrowth from the conjunctiva onto the cornea. S100 proteins are calcium-activated signaling proteins that interact with other proteins to modulate biological functions such as cell migration, proliferation, and differentiation. The aim of this study was to investigate the presence of various S100 proteins in pterygium compared to normal conjunctiva. METHODS: Immunofluorescent staining using antibodies against S100A4, S100A6, S100A8, S100A9, and S100A11 were conducted to investigate the expression and tissue distribution. S100 protein secretions and expressions were confirmed using western blot and quantitative real-time polymerase chain reaction (RT-PCR), respectively. RESULTS: Immunofluorescent staining demonstrated the presence of S100A4, S100A6, S100A8, S100A8, S100A9, and S100A11 in both conjunctival and pterygial epithelium. No significant difference was found in the localization and expression of S100A4. In both conjunctiva and pterygium, S100A4-positive cells were found in superficial and suprabasal layers. S100A6 expression was strong in the superficial layer of pterygium epithelium but relatively weaker in the suprabasal and superficial cells of normal conjunctiva epithelium. S100A8 and S100A9 were localized in the superficial layer of both pterygium and normal conjunctiva epithelium, with higher levels in pterygium than uninvolved conjunctiva. S100A11 was expressed in the basal cells of conjunctival epithelium but in the suprabasal layers of pterygium epithelium. Western blot and RT-PCR confirmed the presence of S100A4, S100A6, S100A8, S100A9, and S100A11 in pterygium and conjunctiva tissue. CONCLUSIONS: Higher levels of S100A6, S100A8, and S100A9 expressions were detected in the pterygium tissue relative to normal conjunctiva. In addition, a distinct alteration of localization of S100A11 expression was observed in pterygium epithelium compared to the conjunctiva. Therefore, these S100 proteins may be associated with the formation of pterygium.
| S-EPMC2642841 | biostudies-literature
Project description:EF-hand Ca2+-binding protein family members, α- and β-parvalbumins have been studied for decades. Yet, considerable information is lacking distinguishing functional differences between mammalian α-parvalbumin (PVALB) and oncomodulin (OCM), a branded β-parvalbumin. Herein, we provide an overview detailing the current body of work centered around OCM as an EF-Hand Ca2+-binding protein and describe potential mechanisms of OCM function within the inner ear and immune cells. Additionally, we posit that OCM is evolutionarily distinct from PVALB and most other β-parvalbumins. This review summarizes recent studies pertaining to the function of OCM and emphasizes OCM as a parvalbumin possessing a unique cell and tissue distribution, Ca2+ buffering capacity and phylogenetic origin.
| S-EPMC6794386 | biostudies-literature
Project description:The crystal structure of rat alpha-parvalbumin has been determined at 1.05 Angstrom resolution, using synchrotron data collected at Advanced Photon Source beamline 19-ID. After refinement with SHELX, employing anisotropic displacement parameters and riding hydrogen atoms, R = 0.132 and R(free) = 0.162. The average coordinate estimated standard deviations are 0.021 Angstrom and 0.038 Angstrom for backbone atoms and side-chain atoms, respectively. Besides providing a more precise view of the alpha-isoform than previously available, these data permit comparison with the 0.91 Angstrom structure determined for pike beta-parvalbumin. Visualization of the anisotropic displacement parameters as thermal ellipsoids yields insight into the atomic motion within the Ca(2+)-binding sites. The asymmetric unit includes three parvalbumin (PV) molecules. Interestingly, the EF site in one displays uncharacteristic flexibility. The ellipsoids for Asp-92 are particularly large and non-spherical, and the shape of the Ca(2+) ellipsoid implies significant vibrational motion perpendicular to the plane defined by the four y and z ligands. The relative dearth of crystal-packing interactions in this site suggests that the heightened flexibility may be the result of diminished intermolecular contacts. The implication is that, by impeding conformational mobility, crystal-packing forces may cause serious overestimation of EF-hand rigidity. The high quality of the data permitted 11 residues to be modeled in alternative side-chain conformations, including the two core residues, Ile-97 and Leu-105. The discrete disorder observed for Ile-97 may have functional ramifications, providing a mechanism for communicating binding status between the CD and EF binding loops and between the PV metal ion-binding domain and the N-terminal AB region.
| S-EPMC2279919 | biostudies-literature
Project description:Parvalbumin (PV) is a cytosolic Ca2+-binding protein highly expressed in fast skeletal muscle, contributing to an increased relaxation rate. Moreover, PV is an "atrogene" downregulated in most muscle atrophy conditions. Here, we exploit mice lacking PV to explore the link between the two PV functions. Surprisingly, PV ablation partially counteracts muscle loss after denervation. Furthermore, acute PV downregulation is accompanied by hypertrophy and upregulation by atrophy. PV ablation has a minor impact on sarcoplasmic reticulum but is associated with increased mitochondrial Ca2+ uptake, mitochondrial size and number, and contacts with Ca2+ release sites. Mitochondrial calcium uniporter (MCU) silencing abolishes the hypertrophic effect of PV ablation, suggesting that mitochondrial Ca2+ uptake is required for hypertrophy. In turn, an increase of mitochondrial Ca2+ is required to enhance expression of the pro-hypertrophy gene PGC-1α4, whose silencing blocks hypertrophy due to PV ablation. These results reveal how PV links cytosolic Ca2+ control to mitochondrial adaptations, leading to muscle mass regulation.
| S-EPMC8113653 | biostudies-literature