The penta-EF hand (PEF) family; The penta-EF hand (PEF) family contains a group of five EF-hand calcium-binding proteins, including several classical calpain large catalytic subunits (CAPN1, 2, 3, 8, 9, 11, 12, 13, 14), two calpain small subunits (CAPNS1 and CAPNS2), as well as non-calpain PEF proteins, ALG-2 (apoptosis-linked gene 2, also termed programmed cell death protein 6, PDCD6), peflin, sorcin, and grancalcin. Based on the sequence similarity of EF1 hand, ALG-2 and peflin have been classified into group I PEF proteins. Calcium-dependent protease calpain subfamily members, sorcin and grancalcin, are group II PEF proteins. Calpains (EC 3.4.22.17) are calcium-activated intracellular cysteine proteases that play important roles in the degradation or functional modulation in a variety of substrates. They have been implicated in a number of physiological processes such as cell cycle progression, remodeling of cytoskeletal-cell membrane attachments, signal transduction, gene expression and apoptosis. ALG-2 is a pro-apoptotic factor that forms a homodimer in the cell or a heterodimer with its closest paralog peflin through their EF5s. Peflin is a 30-kD PEF protein with a longer N-terminal hydrophobic domain than any other member of the PEF family, and it contains nine nonapeptide (A/PPGGPYGGP) repeats. It exists only as a heterodimer with ALG-2. The dissociation of heterodimer occurs in the presence of Ca2+. ALG-2 interacts with various proteins in a Ca2+-dependent manner. Sorcin (for soluble resistance-related calcium binding protein) is a soluble resistance-related calcium-binding protein that participates in the regulation of calcium homeostasis in cells. Grancalcin is a cytosolic Ca2+-binding protein specifically expressed in neutrophils and monocytes/macrophages. It plays a key role in leukocyte-specific functions that are responsible for host defense. Grancalcin can form a heterodimer together with sorcin. Members in this family contain five EF-hand motifs attached to an N-terminal region of variable length containing one or more short Gly/Pro-rich sequences. These proteins form homodimers or heterodimers through pairing between the 5th EF-hands from the two molecules. Unlike calmodulin, the PEF domains do not undergo major conformational changes upon binding Ca2+.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 41473898  33 KTVELLSGVVDQTKDGLISFQEFVA---FESVLCApdalfmvAFQLFDKAGKGEVTFEDVKQVFgqttihQHIPFNWDSE 109
Cdd:cd16185  36 ATAEKLIRMFDRDGNGTIDFEEFAAlhqFLSNMQN-------GFEQRDTSRSGRLDANEVHEAL------AASGFQLDPP 102

                        90       100       110       120       130
                ....*....|....*....|....*....|....*....|....*....|....
gi 41473898 110 FVQ---LHFGKERKRHLTYAEFTQFLLEIQLehAKQAFVQRDNARTGRVTaIDF 160
Cdd:cd16185 103 AFQalfRKFDPDRGGSLGFDDYIELCIFLAS--ARNLFQAFDRQRTGRVT-LDF 153

EF-hand, calcium binding motif, found in homologs of mammalian apoptosis-linked gene 2 protein (ALG-2); The family includes some homologs of mammalian apoptosis-linked gene 2 protein (ALG-2) mainly found in lower eukaryotes, such as a parasitic protist Leishmarua major and a cellular slime mold Dictyostelium discoideum. These homologs contains five EF-hand motifs. Due to the presence of unfavorable residues at the Ca2+-coordinating positions, their non-canonical EF4 and EF5 hands may not bind Ca2+. Two Dictyostelium PEF proteins are the prototypes of this family. They may bind to cytoskeletal proteins and/or signal-transducing proteins localized to detergent-resistant membranes named lipid rafts, and occur as monomers or weak homo- or heterodimers like ALG-2. They can serve as a mediator for Ca2+ signaling-related Dictyostehum programmed cell death (PCD).

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 41473898  33 KTVELLSGVVDQTKDGLISFQEFVA---FESVLCApdalfmvAFQLFDKAGKGEVTFEDVKQVFgqttihQHIPFNWDSE 109
Cdd:cd16185  36 ATAEKLIRMFDRDGNGTIDFEEFAAlhqFLSNMQN-------GFEQRDTSRSGRLDANEVHEAL------AASGFQLDPP 102

                        90       100       110       120       130
                ....*....|....*....|....*....|....*....|....*....|....
gi 41473898 110 FVQ---LHFGKERKRHLTYAEFTQFLLEIQLehAKQAFVQRDNARTGRVTaIDF 160
Cdd:cd16185 103 AFQalfRKFDPDRGGSLGFDDYIELCIFLAS--ARNLFQAFDRQRTGRVT-LDF 153

EF-hand domain pair;

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*..
gi 41473898     3 SIEKNGEFFMSPNDFVtRYLNIFGESQP-NPKTVELLSGVVDQTKDGLISFQEFVAF 58
Cdd:pfam13499  10 LLDSDGDGYLDVEELK-KLLRKLEEGEPlSDEEVEELFKEFDLDKDGRISFEEFLEL 65

EF-hand, calcium binding motif, found in homologs of mammalian apoptosis-linked gene 2 protein (ALG-2); The family includes some homologs of mammalian apoptosis-linked gene 2 protein (ALG-2) mainly found in lower eukaryotes, such as a parasitic protist Leishmarua major and a cellular slime mold Dictyostelium discoideum. These homologs contains five EF-hand motifs. Due to the presence of unfavorable residues at the Ca2+-coordinating positions, their non-canonical EF4 and EF5 hands may not bind Ca2+. Two Dictyostelium PEF proteins are the prototypes of this family. They may bind to cytoskeletal proteins and/or signal-transducing proteins localized to detergent-resistant membranes named lipid rafts, and occur as monomers or weak homo- or heterodimers like ALG-2. They can serve as a mediator for Ca2+ signaling-related Dictyostehum programmed cell death (PCD).

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 41473898  33 KTVELLSGVVDQTKDGLISFQEFVA---FESVLCApdalfmvAFQLFDKAGKGEVTFEDVKQVFgqttihQHIPFNWDSE 109
Cdd:cd16185  36 ATAEKLIRMFDRDGNGTIDFEEFAAlhqFLSNMQN-------GFEQRDTSRSGRLDANEVHEAL------AASGFQLDPP 102

                        90       100       110       120       130
                ....*....|....*....|....*....|....*....|....*....|....
gi 41473898 110 FVQ---LHFGKERKRHLTYAEFTQFLLEIQLehAKQAFVQRDNARTGRVTaIDF 160
Cdd:cd16185 103 AFQalfRKFDPDRGGSLGFDDYIELCIFLAS--ARNLFQAFDRQRTGRVT-LDF 153

Ca2+-binding protein, EF-hand superfamily [Signal transduction mechanisms];

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 41473898   7 NGEFFMSPNDFVTRYLNIFGESQPNpkTVELLSGVVDQTKDGLISFQEFVAFESVLCAPDALFMVAFQLFDKAGKGEVTF 86
Cdd:COG5126  45 DGDGRISREEFVAGMESLFEATVEP--FARAAFDLLDTDGDGKISADEFRRLLTALGVSEEEADELFARLDTDGDGKISF 122

                ....*....
gi 41473898  87 EDVKQVFGQ 95
Cdd:COG5126 123 EEFVAAVRD 131

EF-hand motif found in eukaryotic phosphoinositide-specific phospholipase C (PI-PLC, EC 3.1.4.11) isozymes; PI-PLC isozymes are signaling enzymes that hydrolyze the membrane phospholipids phosphatidylinositol-4,5-bisphosphate (PIP2) to generate two important second messengers in eukaryotic signal transduction cascades, Inositol 1,4,5-trisphosphate (InsP3) and diacylglycerol (DAG). InsP3 triggers inflow of calcium from intracellular stores, while DAG, together with calcium, activates protein kinase C, which goes on to phosphorylate other molecules, leading to altered cellular activity. Calcium is required for the catalysis. This family corresponds to the four EF-hand motifs containing PI-PLC isozymes, including PI-PLC-beta (1-4), -gamma (1-2), -delta (1,3,4), -epsilon (1), -zeta (1), eta (1-2). Lower eukaryotes such as yeast and slime molds contain only delta-type isozymes. In contrast, other types of isoforms present in higher eukaryotes. This family also includes 1-phosphatidylinositol 4,5-bisphosphate phosphodiesterase 1 (PLC1) from fungi. Some homologs from plants contain only two atypical EF-hand motifs and they are not included. All PI-PLC isozymes except sperm-specific PI-PLC-zeta share a core set of domains, including an N-terminal pleckstrin homology (PH) domain, four atypical EF-hand motifs, a PLC catalytic core, and a single C2 domain. PI-PLC-zeta lacks the PH domain. The PLC catalytic core domain is a TIM barrel with two highly conserved regions (X and Y) split by a highly degenerate linker sequence. Most of EF-hand motifs found in PI-PLCs consist of a helix-loop-helix structure, but lack residues critical to metal binding. Moreover, the EF-hand region of most of PI-PLCs may have an important regulatory function, but it has yet to be identified. However, PI-PLC-zeta is a key exception. It is responsible for Ca2+ oscillations in fertilized oocytes and exhibits a high sensitivity to Ca2+ mediated through its EF-hand domain. In addition, PI-PLC-eta2 shows a canonical EF-loop directing Ca2+-sensitivity and thus can amplify transient Ca2+ signals. Also it appears that PI-PLC-delta1 can regulate the binding of PH domain to PIP2 in a Ca2+-dependent manner through its functionally important EF-hand domains. PI-PLCs can be activated by a variety of extracellular ligands, such as growth factors, hormones, cytokines and lipids. Their activation has been implicated in tumorigenesis and/or metastasis linked to migration, proliferation, growth, inflammation, angiogenesis and actin cytoskeleton reorganization. PI-PLC-beta isozymes are activated by G-protein coupled receptor (GPCR) through different mechanisms. However, PI-PLC-gamma isozymes are activated by receptor tyrosine kinase (RTK), such as Rho and Ras GTPases. In contrast, PI-PLC-epsilon are activated by both GPCR and RTK. PI-PLC-delta1 and PLC-eta 1 are activated by GPCR-mediated calcium mobilization. The activation mechanism for PI-PLC-zeta remains unclear.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 41473898  42 VDQTKDGLISFQEFVAFESVL--CAPDALFMVAFQLFDKAGKGEVTFEDVKQVFGQTTIHQHIpfnwdsEFVQLHFGKER 119
Cdd:cd15898   9 ADKDGDGKLSLKEIKKLLKRLniRVSEKELKKLFKEVDTNGDGTLTFDEFEELYKSLTERPEL------EPIFKKYAGTN 82

                        90       100
                ....*....|....*....|
gi 41473898 120 KRHLTYAEFTQFLLEIQLEH 139
Cdd:cd15898  83 RDYMTLEEFIRFLREEQGEN 102