Alpha crystallin domain (ACD) found in Saccharomyces cerevisiae (Sc) small heat shock protein (Hsp)26 and similar proteins. sHsps are molecular chaperones that suppress protein aggregation and protect against cell stress, and are generally active as large oligomers consisting of multiple subunits. ScHsp26 is temperature-regulated, it switches from an inactive to a chaperone-active form upon elevation in temperature. It associates into large 24-mers storage forms which upon heat shock disassociate into dimers. These dimers initiate the interaction with non-native substrate proteins and re-assemble into large globular assemblies having one monomer of substrate bound per dimer. This group also contains Arabidopsis thaliana (Ath) Hsp15.7, a peroxisomal matrix protein which can complement the morphological phenotype of S. cerevisiae mutants deficient in Hsps26. AthHsp15.7 is minimally expressed under normal conditions and is strongly induced by heat and oxidative stress. Also belonging to this group is wheat HSP16.9 which differs in quaternary structure from the shell-type particles of ScHsp26, it assembles as a dodecameric double disc, with each disc organized as a trimer of dimers.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 3695402   72 RVDWKETAEGHEIMLDIPGLKKDEVKIEVEENGVLRVSGERKREEEKKGDQWHRVERSYGKFWRQFKLPDNVDMESVKAK 151
Cdd:cd06472   1 RVDWKETPEAHVFKADVPGVKKEDVKVEVEDGRVLRISGERKKEEEKKGDDWHRVERSSGRFVRRFRLPENADADEVKAF 80

                        90
                ....*....|..
gi 3695402  152 LENGVLTINLTK 163
Cdd:cd06472  81 LENGVLTVTVPK 92

Alpha crystallin domain (ACD) found in Saccharomyces cerevisiae (Sc) small heat shock protein (Hsp)26 and similar proteins. sHsps are molecular chaperones that suppress protein aggregation and protect against cell stress, and are generally active as large oligomers consisting of multiple subunits. ScHsp26 is temperature-regulated, it switches from an inactive to a chaperone-active form upon elevation in temperature. It associates into large 24-mers storage forms which upon heat shock disassociate into dimers. These dimers initiate the interaction with non-native substrate proteins and re-assemble into large globular assemblies having one monomer of substrate bound per dimer. This group also contains Arabidopsis thaliana (Ath) Hsp15.7, a peroxisomal matrix protein which can complement the morphological phenotype of S. cerevisiae mutants deficient in Hsps26. AthHsp15.7 is minimally expressed under normal conditions and is strongly induced by heat and oxidative stress. Also belonging to this group is wheat HSP16.9 which differs in quaternary structure from the shell-type particles of ScHsp26, it assembles as a dodecameric double disc, with each disc organized as a trimer of dimers.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 3695402   72 RVDWKETAEGHEIMLDIPGLKKDEVKIEVEENGVLRVSGERKREEEKKGDQWHRVERSYGKFWRQFKLPDNVDMESVKAK 151
Cdd:cd06472   1 RVDWKETPEAHVFKADVPGVKKEDVKVEVEDGRVLRISGERKKEEEKKGDDWHRVERSSGRFVRRFRLPENADADEVKAF 80

                        90
                ....*....|..
gi 3695402  152 LENGVLTINLTK 163
Cdd:cd06472  81 LENGVLTVTVPK 92

Hsp20/alpha crystallin family; Not only do small heat-shock-proteins occur in eukaryotes and prokaryotes but they have also now been shown to occur in cyanobacterial phages as well as their bacterial hosts.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 3695402     74 DWKETAEGHEIMLDIPGLKKDEVKIEVEENGVLRVSgerKREEEKKGDQWHRVERSYGKFWRQFKLPDNVDMESVKAKLE 153
Cdd:pfam00011   1 DIKEDEDAFEVRLDVPGFKPEELKVKVEDNRLLVKG---EHEEEKEDDHGLRSERSYGSFSRKFTLPENADPDKVKASLK 77

                          90       100
                  ....*....|....*....|....
gi 3695402    154 NGVLTINLTKLSPEkvKGPRVVNI 177
Cdd:pfam00011  78 DGVLTVTVPKLEPE--PKERRIQI 99

Alpha crystallin domain (ACD) found in Saccharomyces cerevisiae (Sc) small heat shock protein (Hsp)26 and similar proteins. sHsps are molecular chaperones that suppress protein aggregation and protect against cell stress, and are generally active as large oligomers consisting of multiple subunits. ScHsp26 is temperature-regulated, it switches from an inactive to a chaperone-active form upon elevation in temperature. It associates into large 24-mers storage forms which upon heat shock disassociate into dimers. These dimers initiate the interaction with non-native substrate proteins and re-assemble into large globular assemblies having one monomer of substrate bound per dimer. This group also contains Arabidopsis thaliana (Ath) Hsp15.7, a peroxisomal matrix protein which can complement the morphological phenotype of S. cerevisiae mutants deficient in Hsps26. AthHsp15.7 is minimally expressed under normal conditions and is strongly induced by heat and oxidative stress. Also belonging to this group is wheat HSP16.9 which differs in quaternary structure from the shell-type particles of ScHsp26, it assembles as a dodecameric double disc, with each disc organized as a trimer of dimers.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 3695402   72 RVDWKETAEGHEIMLDIPGLKKDEVKIEVEENGVLRVSGERKREEEKKGDQWHRVERSYGKFWRQFKLPDNVDMESVKAK 151
Cdd:cd06472   1 RVDWKETPEAHVFKADVPGVKKEDVKVEVEDGRVLRISGERKKEEEKKGDDWHRVERSSGRFVRRFRLPENADADEVKAF 80

                        90
                ....*....|..
gi 3695402  152 LENGVLTINLTK 163
Cdd:cd06472  81 LENGVLTVTVPK 92

Hsp20/alpha crystallin family; Not only do small heat-shock-proteins occur in eukaryotes and prokaryotes but they have also now been shown to occur in cyanobacterial phages as well as their bacterial hosts.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 3695402     74 DWKETAEGHEIMLDIPGLKKDEVKIEVEENGVLRVSgerKREEEKKGDQWHRVERSYGKFWRQFKLPDNVDMESVKAKLE 153
Cdd:pfam00011   1 DIKEDEDAFEVRLDVPGFKPEELKVKVEDNRLLVKG---EHEEEKEDDHGLRSERSYGSFSRKFTLPENADPDKVKASLK 77

                          90       100
                  ....*....|....*....|....
gi 3695402    154 NGVLTINLTKLSPEkvKGPRVVNI 177
Cdd:pfam00011  78 DGVLTVTVPKLEPE--PKERRIQI 99

This domain family includes the alpha-crystallin domain (ACD) of alpha-crystallin-type small heat shock proteins (sHsps) and a similar domain found in p23-like proteins. sHsps are small stress induced proteins with monomeric masses between 12 -43 kDa, whose common feature is this ACD. sHsps are generally active as large oligomers consisting of multiple subunits, and are believed to be ATP-independent chaperones that prevent aggregation and are important in refolding in combination with other Hsps. p23 is a cochaperone of the Hsp90 chaperoning pathway. It binds Hsp90 and participates in the folding of a number of Hsp90 clients including the progesterone receptor. p23 also has a passive chaperoning activity. p23 in addition may act as the cytosolic prostaglandin E2 synthase. Included in this family is the p23-like C-terminal CHORD-SGT1 (CS) domain of suppressor of G2 allele of Skp1 (Sgt1) and the p23-like domains of human butyrate-induced transcript 1 (hB-ind1), NUD (nuclear distribution) C, Melusin, and NAD(P)H cytochrome b5 (NCB5) oxidoreductase (OR).

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 3695402   75 WKETAEGHEIMLDIPGLKKDEVKIEVEENgVLRVSGERKREEEKkgdqwhrvERSYGKFWRQFKLPDNVDMESVKAKLEN 154
Cdd:cd00298   1 WYQTDDEVVVTVDLPGVKKEDIKVEVEDN-VLTISGKREEEEER--------ERSYGEFERSFELPEDVDPEKSKASLEN 71

                ....*....
gi 3695402  155 GVLTINLTK 163
Cdd:cd00298  72 GVLEITLPK 80

Alpha-crystallin domain (ACD) found in Escherichia coli inclusion body-associated proteins IbpA and IbpB, and similar proteins. IbpA and IbpB are 16 kDa small heat shock proteins (sHsps). sHsps are molecular chaperones that suppress protein aggregation and protect against cell stress, and are generally active as large oligomers consisting of multiple subunits. IbpA and IbpB are produced during high-level production of various heterologous proteins, specifically human prorenin, renin and bovine insulin-like growth factor 2 (bIGF-2), and are strongly associated with inclusion bodies containing these heterologous proteins. IbpA and IbpB work as an integrated system to stabilize thermally aggregated proteins in a disaggregation competent state. The chaperone activity of IbpB is also significantly elevated as the temperature increases from normal to heat shock. The high temperature results in the disassociation of 2-3-MDa IbpB oligomers into smaller approximately 600-kDa structures. This elevated activity seen under heat shock conditions is retained for an extended period of time after the temperature is returned to normal. IbpA also forms multimers.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 3695402   82 HEIMLDIPGLKKDEVKIEVEENgVLRVSGERKREEEKKGDQWHRvERSYGKFWRQFKLPDNVdmESVKAKLENGVLTINL 161
Cdd:cd06470  13 YRITLAVAGFSEDDLEIEVENN-QLTVTGKKADEENEEREYLHR-GIAKRAFERSFNLADHV--KVKGAELENGLLTIDL 88

                ..
gi 3695402  162 TK 163
Cdd:cd06470  89 ER 90

Alpha crystallin domain (ACD) found in mammalian small heat shock protein (sHsp) HspB9 and similar proteins. sHsps are molecular chaperones that suppress protein aggregation and protect against cell stress, and are generally active as large oligomers consisting of multiple subunits. Human (h) HspB9 is expressed exclusively in the normal testis and in various tumor samples and is a cancer/testis antigen. hHspB9 interacts with TCTEL1 (T-complex testis expressed protein -1), a subunit of dynein. hHspB9 and TCTEL1 are co-expressed in similar cells within the testis and in tumor cells. Included in this group is Xenopus Hsp30, a developmentally-regulated heat-inducible molecular chaperone.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 3695402   76 KETAEGHEIMLDIPGLKKDEVKIEVEENgVLRVSGERkreEEKKGDQWHRVERSYGKFWRQFKLPDNVDMESVKAKL-EN 154
Cdd:cd06481   3 KDGKEGFSLKLDVRGFSPEDLSVRVDGR-KLVVTGKR---EKKNEDEKGSFSYEYQEFVREAQLPEHVDPEAVTCSLsPS 78

                ....*
gi 3695402  155 GVLTI 159
Cdd:cd06481  79 GHLHI 83

Alpha crystallin domain (ACD) found in mammalian small (s)heat shock protein (Hsp)-27 (also denoted HspB1 in human) and similar proteins. sHsps are molecular chaperones that suppress protein aggregation and protect against cell stress, and are generally active as large oligomers consisting of multiple subunits. Hsp27 shows enhanced synthesis in response to stress. It is a molecular chaperone which interacts with a large number of different proteins. It is found in many types of human cells including breast, uterus, cervix, platelets and cancer cells. Hsp27 has diverse cellular functions including, chaperoning, regulation of actin polymerization, keratinocyte differentiation, regulation of inflammatory pathways in keratinocytes, and protection from oxidative stress through modulating glutathione levels. It is also a subunit of AUF1-containing protein complexes. It has been linked to several transduction pathways regulating cellular functions including differentiation, cell growth, development, and apoptosis. Its activity can be regulated by phosphorylation. Its unphosphorylated state is a high molecular weight aggregated form (100-800kDa) composed of up to 24 subunits, which forms as a result of multiple interactions within the ACD, and is required for chaperone function and resistance to oxidative stress. Upon phosphorylation these large aggregates rapidly disassociate to smaller oligomers and chaperone activity is modified. High constitutive levels of Hsp27 have been detected in various cancer cells, in particular those of carcinoma origin. Over-expression of Hsp27 has a protective effect against various diseases-processes, including Huntington's disease. Mutations in Hsp27 have been associated with a form of distal hereditary motor neuropathy type II and Charcot-Marie-Tooth disease type 2.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 3695402   76 KETAEGHEIMLDIPGLKKDEVKIEVEEnGVLRVSGerkREEEKKgDQWHRVERSygkFWRQFKLPDNVDMESVKAKLE-N 154
Cdd:cd06475   6 RQTADRWKVSLDVNHFAPEELVVKTKD-GVVEITG---KHEEKQ-DEHGFVSRC---FTRKYTLPPGVDPTAVTSSLSpD 77

                ....*
gi 3695402  155 GVLTI 159
Cdd:cd06475  78 GILTV 82