Spiders use fibroins to make silk strands. This family includes tubuliform silk fibroins which are used to protect egg cases. This domain is a structural domain which is found in repeats of up to 20 in many individuals (although this is not necessarily the case). RP1 makes up structural domains in the N-terminal while RP2 makes up structural domains in the C-terminal [].
This is a family of proteins which are putative bifunctional serine/threonine kinase/phosphorylases involved in the regulation of the pyruvate, phosphate dikinase (PPDK) by catalysing its phosphorylation/dephosphorylation [, ]. In plants, the pyruvate, phosphate dikinase regulatory protein 1 (RP1) is a bifunctional serine/threonine kinase and phosphorylase involved in the dark/light-mediated regulation of PPDK by catalysing its phosphorylation/dephosphorylation. In the dark, RP1 phosphorylates the catalytic intermediate of PPDK (PPDK-HisP), inactivating it. Light exposure induces the phosphorolysis reaction that reactivates PPDK [, , , ].
Microtubule-associated protein RP/EB family member 2 (also known as RP1 or EB2) belongs to the RP/EB family, which consists of MAPRE1 (EB1), MAPRE2 (RP1, also known as EB2) and MAPRE3 (EBF3, also known as EB3). Unlike EB1 and EB3, EB2 does not promote persistent microtubule growth by suppressing catastrophes []. It has been shown that MAPRE2 is highly expressed in pancreatic cancer cells, and seems to be involved in perineural invasion [].
Osa and FiwA are fertility inhibition factors (FIN), which are employed by plasmids to block import of rival plasmids []. Osa (oncogenic suppressive activity) of IncW group plasmid pSa gene inhibits the oncogenic properties of Agrobacterium tumefaciens. Osa is structurally similar to the ParB N-terminal domain/Srx superfamily of proteins: ParB acts in the bacterial and plasmid parABS partitioning systems []. Osa has been shown to have ATPase and DNAse activities, and can block T-DNA transfer into plants [, ]. FiwA is encoded by plasmid RP1 and blocks the transfer of plasmid R388 []. The gene product of Haemophilus influenzae p1056.10c also blocks T-DNA transfer [].
X-linked lissencephaly is a severe brain malformation affecting males. Recently it has been demonstrated that the doublecortin gene is implicated in this disorder []. Doublecortin was found to bind to the microtubule cytoskeleton. In vivo and in vitro assays show that Doublecortin stabilises microtubules and causes bundling []. Doublecortin is a basic protein with an iso-electric point of 10, typical of microtubule-binding proteins. However, its sequence contains no known microtubule-binding domain(s).The detailed sequence analysis of Doublecortin and Doublecortin-like proteins allowed the identification of an evolutionarily conserved Doublecortin (DC) domain, which is ubiquitin-like. This domain is found in the N terminus of proteins and consists of one or two tandemly repeated copies of an around 80 amino acids region. It has been suggested that the first DC domain of Doublecortin binds tubulin and enhances microtubule polymerisation [].Some proteins known to contain a DC domain are listed below:Doublecortin. It is required for neuronal migration []. A large number of point mutations in the human DCX gene leading to lissencephaly are located within the DC domains [].Human serine/threonine-protein kinase DCAMKL1. It is a probable kinase that may be involved in a calcium-signaling pathway controlling neuronal migration in the developing brain [, ].Retinitis pigmentosa 1 protein. It is required for the differentiation of photoreceptor cells. Mutation in the human RP1 gene cause retinitis pigmentosa of type 1 [, ].
This entry includes oxygen-regulated protein 1 (RP1), retinitis pigmentosa 1-like 1 (RP1L1) and neuronal migration protein doublecortin (DCX).Oxygen-regulated protein 1 (also known as retinitis pigmentosa 1, RP1) is a photoreceptor-specific, microtubule-associated ciliary protein containing the doublecortin (DCX) domain. Together with RP1L1, they play essential and synergistic roles in affecting photosensitivity and outer segment morphogenesis of rod photoreceptors [].Mutations in the RP1 gene account for 5-10% of cases of autosomal dominant retinitis pigmentosa, a disease characterised by late-onset night blindness, loss of peripheral vision, and diminished or absent electroretinogram (ERG) responses [].Mutations in the RP1L1 gene cause occult macular dystrophy (OCMD), an inherited macular dystrophy characterised by progressive loss of macular function but normal ophthalmoscopic appearance []. Neuronal migration protein doublecortin (DCX; also known as Lissencephalin-X) seems to be required for the initial steps of neuronal dispersion and cortex lamination during cerebral cortex development []. This protein may act by competing with the putative neuronal protein kinase DCAMKL1 in binding to a target protein, and thereby participate in a signalling pathway that is crucial for neuronal interaction before and during migration, possibly as part of a calcium ion-dependent signal transduction pathway. It may also be involved with LIS-1 in an overlapping, but distinct, signalling pathways that promotes neuronal migration. Defects in neuronal migration protein doublecortin are the cause of lissencephaly X-linked type 1 (LISX1), a classic lissencephaly characterised by mental retardation and seizures that are more severe in male patients [, ].
X-linked lissencephaly is a severe brain malformation affecting males. Recently it has been demonstrated that the doublecortin gene is implicated in this disorder []. Doublecortin was found to bind to the microtubule cytoskeleton. In vivo and in vitro assays show that Doublecortin stabilises microtubules and causes bundling []. Doublecortin is a basic protein with an iso-electric point of 10, typical of microtubule-binding proteins. However, its sequence contains no known microtubule-binding domain(s).The detailed sequence analysis of Doublecortin and Doublecortin-like proteins allowed the identification of an evolutionarily conserved Doublecortin (DC) domain, which is ubiquitin-like. This domain is found in the N terminus of proteins and consists of one or two tandemly repeated copies of an around 80 amino acids region. It has been suggested that the first DC domain of Doublecortin binds tubulin and enhances microtubule polymerisation [].Some proteins known to contain a DC domain are listed below:Doublecortin. It is required for neuronal migration []. A large number of point mutations in the human DCX gene leading to lissencephaly are located within the DC domains [].Human serine/threonine-protein kinase DCAMKL1. It is a probable kinase that may be involved in a calcium-signaling pathway controlling neuronal migration in the developing brain [, ].Retinitis pigmentosa 1 protein. It is required for the differentiation of photoreceptor cells. Mutation in the human RP1 gene cause retinitis pigmentosa of type 1 [, ].
Spidroins are large silk proteins which display relatively conserved terminal domains and a characteristic core repetitive region that amounts to around 90 % of the full length sequence and is believed to dominate the mechanical properties of spider silk. Spidroins are secreted into silk glands and then stably stored where their concentration increases up to 50 % (w/w) allowing them to self-assemble into silk fibres. Spider silks are renowned for their excellent mechanical properties and biomimetic and industrial potentials. The orb-web spiders employ up to seven types of abdominal glands to produce silks for various purposes, ranging from prey capture to offspring protection in egg cases. Egg-case silk fibroins are synthesised only in female tubuliform (cylindrical) silk glands for the construction of protective egg cases, where eggs undergo development. Two spidroins, tubliform spidroin (TuSp1), the major component of egg-case silk, and the recently characterised aciniform spidroin (AcSp1) participate in the egg case formation: AcSp1 forms the inner egg case, while TuSp1 forms the outer egg case. Studies on both proteins have revealed poor sequence similarity between their respective repetitive (RP) domains but a remarkable structural identity. The latter suggests that these two spidroins may share some common characters in fibre formation mechanism and silk fibre properties [, ].This superfamily represents a structural domain which is found in repeats of up to 20 in many individuals (although this is not necessarily the case). RP1 makes up structural domains in the N terminus while RP2 makes up structural domains in the C terminus [].
