Phosducin (Phd)-like family, Phd subfamily; Phd is a cytosolic regulator of G protein functions. It specifically binds G protein betagamma (Gbg)-subunits with high affinity, resulting in the solubilization of Gbg from the plasma membrane. This impedes the formation of a functional G protein trimer (G protein alphabetagamma), thereby inhibiting G protein-mediated signal transduction. Phd also inhibits the GTPase activity of G protein alpha. Phd can be phosphorylated by protein kinase A and G protein-coupled receptor kinase 2, leading to its inactivation. Phd was originally isolated from the retina, where it is highly expressed and has been implicated to play an important role in light adaptation. It is also found in the pineal gland, liver, spleen, striated muscle and the brain. The C-terminal domain of Phd adopts a thioredoxin fold, but it does not contain a CXXC motif. Phd interacts with G protein beta mostly through the N-terminal helical domain.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2288557266   1 YRKRCMQDMHQWLSFGPKYGSLSELQSGEQFLETI*KERKTTTVIVHIYEHAVKGCDLLNSSLTCLAAEYSMVRFCKIKA 80
Cdd:cd02987    43 YREQRMQEMHAKLPFGRRFGKVYELDSGEQFLDAIDKEGKDTTVVVHIYEPGIPGCAALNSSLLCLAAEYPAVKFCKIRA 122

                          90       100       110
                  ....*....|....*....|....*....|....*..
gi 2288557266  81 SNTGAEDRFSSDVLPTLLVYRGGELVSNFLSVTEQFN 117
Cdd:cd02987   123 SATGASDEFDTDALPALLVYKGGELIGNFVRVTEDLG 159

Phosducin (Phd)-like family, Phd subfamily; Phd is a cytosolic regulator of G protein functions. It specifically binds G protein betagamma (Gbg)-subunits with high affinity, resulting in the solubilization of Gbg from the plasma membrane. This impedes the formation of a functional G protein trimer (G protein alphabetagamma), thereby inhibiting G protein-mediated signal transduction. Phd also inhibits the GTPase activity of G protein alpha. Phd can be phosphorylated by protein kinase A and G protein-coupled receptor kinase 2, leading to its inactivation. Phd was originally isolated from the retina, where it is highly expressed and has been implicated to play an important role in light adaptation. It is also found in the pineal gland, liver, spleen, striated muscle and the brain. The C-terminal domain of Phd adopts a thioredoxin fold, but it does not contain a CXXC motif. Phd interacts with G protein beta mostly through the N-terminal helical domain.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2288557266   1 YRKRCMQDMHQWLSFGPKYGSLSELQSGEQFLETI*KERKTTTVIVHIYEHAVKGCDLLNSSLTCLAAEYSMVRFCKIKA 80
Cdd:cd02987    43 YREQRMQEMHAKLPFGRRFGKVYELDSGEQFLDAIDKEGKDTTVVVHIYEPGIPGCAALNSSLLCLAAEYPAVKFCKIRA 122

                          90       100       110
                  ....*....|....*....|....*....|....*..
gi 2288557266  81 SNTGAEDRFSSDVLPTLLVYRGGELVSNFLSVTEQFN 117
Cdd:cd02987   123 SATGASDEFDTDALPALLVYKGGELIGNFVRVTEDLG 159

Phosducin (Phd)-like family, Viral inhibitor of apoptosis (IAP)-associated factor (VIAF) subfamily; VIAF is a Phd-like protein that functions in caspase activation during apoptosis. It was identified as an IAP binding protein through a screen of a human B-cell library using a prototype IAP. VIAF lacks a consensus IAP binding motif and while it does not function as an IAP antagonist, it still plays a regulatory role in the complete activation of caspases. VIAF itself is a substrate for IAP-mediated ubiquitination, suggesting that it may be a target of IAPs in the prevention of cell death. The similarity of VIAF to Phd points to a potential role distinct from apoptosis regulation. Phd functions as a cytosolic regulator of G protein by specifically binding to G protein betagamma (Gbg)-subunits. The C-terminal domain of Phd adopts a thioredoxin fold, but it does not contain a CXXC motif. Phd interacts with G protein beta mostly through the N-terminal helical domain.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2288557266   1 YRKRCMQDMHQwLSFGPKYGSLSELqSGEQFLETI*KERKTTTVIVHIYEHAVKGCDLLNSSLTCLAAEYSMVRFCKIkA 80
Cdd:cd02988    64 YRRKRLAEMKA-LAEKSKFGEVYEI-SKPDYVREVTEASKDTWVVVHLYKDGIPLCRLLNQHLSELARKFPDTKFVKI-I 140

                          90       100       110
                  ....*....|....*....|....*....|....
gi 2288557266  81 SNTGAEDrFSSDVLPTLLVYRGGELVSNFLSVTE 114
Cdd:cd02988   141 STQCIPN-YPDKNLPTILVYRNGDIVKQFIGLLE 173

TRX family; composed of two groups: Group I, which includes proteins that exclusively encode a TRX domain; and Group II, which are composed of fusion proteins of TRX and additional domains. Group I TRX is a small ancient protein that alter the redox state of target proteins via the reversible oxidation of an active site dithiol, present in a CXXC motif, partially exposed at the protein's surface. TRX reduces protein disulfide bonds, resulting in a disulfide bond at its active site. Oxidized TRX is converted to the active form by TRX reductase, using reducing equivalents derived from either NADPH or ferredoxins. By altering their redox state, TRX regulates the functions of at least 30 target proteins, some of which are enzymes and transcription factors. It also plays an important role in the defense against oxidative stress by directly reducing hydrogen peroxide and certain radicals, and by serving as a reductant for peroxiredoxins. At least two major types of functional TRXs have been reported in most organisms; in eukaryotes, they are located in the cytoplasm and the mitochondria. Higher plants contain more types (at least 20 TRX genes have been detected in the genome of Arabidopsis thaliana), two of which (types f amd m) are located in the same compartment, the chloroplast. Also included in the alignment are TRX-like domains which show sequence homology to TRX but do not contain the redox active CXXC motif. Group II proteins, in addition to either a redox active TRX or a TRX-like domain, also contain additional domains, which may or may not possess homology to known proteins.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2288557266  29 EQFLETI*KERKtttVIVHIY----EHavkgCDLLNSSLTCLAAEYSMVRFCKIkasNTGAEDRFSSD----VLPTLLVY 100
Cdd:cd02947     1 EEFEELIKSAKP---VVVDFWapwcGP----CKAIAPVLEELAEEYPKVKFVKV---DVDENPELAEEygvrSIPTFLFF 70

                  ....*.
gi 2288557266 101 RGGELV 106
Cdd:cd02947    71 KNGKEV 76