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 215693966  29 FAALDTNRDGLLSYAEMANELMS----------LRVLDKHFGVDEAA-MGADELVELYH------GLFLRFDRDGSGAVD 91
Cdd:cd16180    6 FQAVDRDRSGRISAKELQRALSNgdwtpfsietVRLMINMFDRDRSGtINFDEFVGLWKyiqdwrRLFRRFDRDRSGSID 85

                         90       100
                 ....*....|....*....|....*...
gi 215693966  92 LEEFRAEMkevllavaNGLGF-LPVQMV 118
Cdd:cd16180   86 FNELQNAL--------SSFGYrLSPQFV 105

Penta-EF hand, calcium binding motifs, found in Group I PEF proteins; The family corresponds to Group I PEF proteins that have been found not only in higher animals but also in lower animals, plants, fungi and protists. Group I PEF proteins include apoptosis-linked gene 2 protein (ALG-2), peflin and similar proteins. ALG-2, also termed programmed cell death protein 6 (PDCD6), is a widely expressed calcium-binding modulator protein associated with cell proliferation and death, as well as cell survival. It forms a homodimer in the cell or a heterodimer with its closest paralog peflin. Among the PEF proteins, ALG-2 can bind three Ca2+ ions through its EF1, EF3, and EF5 hands, where it is unique in that its EF5 hand binds Ca2+ ion in a canonical coordination. Peflin is a ubiquitously expressed 30-kD PEF protein containing five EF-hand motifs in its C-terminal domain and a longer N-terminal hydrophobic domain (NHB domain) than any other member of the PEF family. The NHB domain harbors nine repeats of a nonapeptide (A/PPGGPYGGP). Peflin may modulate the function of ALG-2 in Ca2+ signaling. It exists only as a heterodimer with ALG-2, and binds two Ca2+ ions through its EF1 and EF3 hands. Its additional EF5 hand is unpaired and does not bind Ca2+ ion but mediates the heterodimerization with ALG-2. The dissociation of heterodimer occurs in the presence of Ca2+.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 215693966  29 FAALDTNRDGLLSYAEMANELMS----------LRVLDKHFGVDEAA-MGADELVELYH------GLFLRFDRDGSGAVD 91
Cdd:cd16180    6 FQAVDRDRSGRISAKELQRALSNgdwtpfsietVRLMINMFDRDRSGtINFDEFVGLWKyiqdwrRLFRRFDRDRSGSID 85

                         90       100
                 ....*....|....*....|....*...
gi 215693966  92 LEEFRAEMkevllavaNGLGF-LPVQMV 118
Cdd:cd16180   86 FNELQNAL--------SSFGYrLSPQFV 105

EF-hand domain pair;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|...
gi 215693966   28 RFAALDTNRDGLLSYAEMANelmSLRVLDKHFGVDeaamgaDELVELyhgLFLRFDRDGSGAVDLEEFRAEMK 100
Cdd:pfam13499   7 AFKLLDSDGDGYLDVEELKK---LLRKLEEGEPLS------DEEVEE---LFKEFDLDKDGRISFEEFLELYS 67

Penta-EF hand, calcium binding motifs, found in Group I PEF proteins; The family corresponds to Group I PEF proteins that have been found not only in higher animals but also in lower animals, plants, fungi and protists. Group I PEF proteins include apoptosis-linked gene 2 protein (ALG-2), peflin and similar proteins. ALG-2, also termed programmed cell death protein 6 (PDCD6), is a widely expressed calcium-binding modulator protein associated with cell proliferation and death, as well as cell survival. It forms a homodimer in the cell or a heterodimer with its closest paralog peflin. Among the PEF proteins, ALG-2 can bind three Ca2+ ions through its EF1, EF3, and EF5 hands, where it is unique in that its EF5 hand binds Ca2+ ion in a canonical coordination. Peflin is a ubiquitously expressed 30-kD PEF protein containing five EF-hand motifs in its C-terminal domain and a longer N-terminal hydrophobic domain (NHB domain) than any other member of the PEF family. The NHB domain harbors nine repeats of a nonapeptide (A/PPGGPYGGP). Peflin may modulate the function of ALG-2 in Ca2+ signaling. It exists only as a heterodimer with ALG-2, and binds two Ca2+ ions through its EF1 and EF3 hands. Its additional EF5 hand is unpaired and does not bind Ca2+ ion but mediates the heterodimerization with ALG-2. The dissociation of heterodimer occurs in the presence of Ca2+.

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 215693966  29 FAALDTNRDGLLSYAEMANELMS----------LRVLDKHFGVDEAA-MGADELVELYH------GLFLRFDRDGSGAVD 91
Cdd:cd16180    6 FQAVDRDRSGRISAKELQRALSNgdwtpfsietVRLMINMFDRDRSGtINFDEFVGLWKyiqdwrRLFRRFDRDRSGSID 85

                         90       100
                 ....*....|....*....|....*...
gi 215693966  92 LEEFRAEMkevllavaNGLGF-LPVQMV 118
Cdd:cd16180   86 FNELQNAL--------SSFGYrLSPQFV 105

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

                         10        20        30        40        50        60        70        80
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 215693966  28 RFAALDTNRDGLLSYAEMANELMSL--RVLDKHFGVDEAAMGADELVELYHGLFLR------------FDRDGSGAVDLE 93
Cdd:COG5126   10 RFDLLDADGDGVLERDDFEALFRRLwaTLFSEADTDGDGRISREEFVAGMESLFEAtvepfaraafdlLDTDGDGKISAD 89

                 ....*...
gi 215693966  94 EFRAEMKE 101
Cdd:COG5126   90 EFRRLLTA 97

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 215693966   7 DGKTVLSFVEDEG--AFNSSVDGRFAALDTNRDGLLSYAEMANELMSLrvldkHFGVDEAAmgadelvelYHGLFLRFDR 84
Cdd:cd16185   48 DGNGTIDFEEFAAlhQFLSNMQNGFEQRDTSRSGRLDANEVHEALAAS-----GFQLDPPA---------FQALFRKFDP 113

                         90
                 ....*....|.
gi 215693966  85 DGSGAVDLEEF 95
Cdd:cd16185  114 DRGGSLGFDDY 124

EF-hand, calcium binding motif; A diverse superfamily of calcium sensors and calcium signal modulators; most examples in this alignment model have 2 active canonical EF hands. Ca2+ binding induces a conformational change in the EF-hand motif, leading to the activation or inactivation of target proteins. EF-hands tend to occur in pairs or higher copy numbers.

                         10        20        30        40        50        60        70
                 ....*....|....*....|....*....|....*....|....*....|....*....|....*....|..
gi 215693966  29 FAALDTNRDGLLSYAEMAnELMSlrvldkhfgvdeaAMGADELVELYHGLFLRFDRDGSGAVDLEEFRAEMK 100
Cdd:cd00051    6 FRLFDKDGDGTISADELK-AALK-------------SLGEGLSEEEIDEMIREVDKDGDGKIDFEEFLELMA 63