The myelin sheath is a multi-layered membrane, unique to the nervous system, that functions as an insulator to greatly increase the velocity of axonal impulse conduction []. Myelin basic protein (MBP) [, ]is a hydrophilic protein that may function to maintain the correct structure of myelin, interacting with the lipids in the myelin membrane by electrostatic and hydrophobic interactions. In mammals various forms of MBP exist which are produced by the alternative splicing of a single gene; these forms differ by the presence or the absence of short (10 to 20 residues) peptidesin various internal locations in the sequence. The major form of MBP is generally a protein of about 18.5 Kd (170 residues). MBP is the target of many post-translational modifications: it is N-terminally acetylated, methylated on an arginine residue, phosphorylated by various serine/threonine protein-kinases, and deamidated on some glutamine residues.
This entry represents the RNA recognition motif 1 (RRM1) of MEF-2 (also known as MyEF-2), a sequence-specific single-stranded DNA (ssDNA) binding protein that binds specifically to ssDNA derived from the proximal (MB1) element of the myelin basic protein (MBP) promoter and represses transcription of the MBP gene [, ]. MEF-2 contains three RNA recognition motifs (RRMs).
This entry represents the RNA recognition motif 3 (RRM3) of MEF-2 (also known as MyEF-2), a sequence-specific single-stranded DNA (ssDNA) binding protein that binds specifically to ssDNA derived from the proximal (MB1) element of the myelin basic protein (MBP) promoter and represses transcription of the MBP gene [, ]. MEF-2 contains three RNA recognition motifs (RRMs).
Eosinophil granule major basic protein (MBP) is a low molecular weight cationic protein present in the crystalloid core of the eosinophil granule[]. It is a potent toxin for helminths and mammalian cells, and may have important roles in allergic and inflammatory reactions, it can release histamine from mast cells and damage epithelial cells of bronchial tubes.MBP is also involved in antiparasitic defence mechanisms and immune hypersensitivity reactions. The protein is a single arginine-rich polypeptide[], its pro-portion being rich in glutamic and aspartic acids. It has been suggested that the protein is translated as a nontoxic precursor that protects the eosinophil from damage while it is processed through the endoplasmic reticulum to its sequestered site in the granule core toxic MBP []. The sequence of MBP has been shown to contain a C-type lectin (CTL) domain []. CTL domains are 110-130 residue motifs that appear to function as calcium-dependent carbohydrate-recognition domains [, , ].
MEF-2 (also known as MyEF-2) is a sequence-specific single-stranded DNA (ssDNA) binding protein that binds specifically to ssDNA derived from the proximal (MB1) element of the myelin basic protein (MBP) promoter and represses transcription of the MBP gene [, ]. MEF-2 contains two RNA recognition motifs (RRMs). MEF-2 is also a binding partner of RUNX1 during erythropoiesis, which is bound in undifferentiated cells and lost upon differentiation [].
This entry represents metazoan myelin gene regulatory factor (MRF). MRF is a transcription regulator required in vertebrates for expression of central nervous system (CNS) myelin genes such as Mbp and Mog, thereby playing a central role in oligodendrocyte maturation and CNS myelination []. It is also required for the maintenance of expression of myelin genes and the mature oligodendrocytes identity in the adult CNS []. A Caenorhabditis elegans orthologue, pqn-47, may function as a regulator of molting [], while a Dictyostelium orthologue has been described to regulate prestalk differentiation [].
Myelin regulatory factor (Myrf) is a transcription regulator required in vertebrates for expression of central nervous system (CNS) myelin genes such as Mbp and Mog, thereby playing a central role in oligodendrocyte maturation and CNS myelination []. It is also required for the maintenance of expression of myelin genes and the mature oligodendrocytes identity in the adult CNS [, ]. A Caenorhabditis elegans orthologue, pqn-47, may function as a regulator of molting [], while a Dictyostelium orthologue has been described to regulate prestalk differentiation [].This domain is found at the C terminus of myelin regulatory factor. The function of the domain is not known.
This entry represents the C-type lectin-like domain (CTLD) of the type found in human collectins including lung surfactant proteins A and D, mannose-binding lectin (MBL, also known as mannan-binding protein or MBP), and CL-L1 (collectin liver 1) [, ]. CTLD refers to a domain, homologous to the carbohydrate-recognition domains (CRDs) of the C-type lectins [].The CTLDs of these collectins bind carbohydrates on surfaces (e.g. pathogens, allergens, necrotic, or apoptotic cells) and mediate functions associated with killing and phagocytosis. MBPs recognize high mannose oligosaccharides in a calcium dependent manner, bind to a broad range of pathogens, and trigger cell killing by activating the complement pathway [, ]. MBP also acts directly as an opsonin []. SP-A and SP-D in addition to functioning as host defense components, are components of pulmonary surfactant which play a role in surfactant homeostasis [, ]. Pulmonary surfactant is a phospholipid-protein complex which reduces the surface tension within the lungs. SP-A binds the major surfactant lipid: dipalmitoylphosphatidylcholine (DPPC). SP-D binds two minor components of surfactant that contain sugar moieties: glucosylceramide and phosphatidylinositol (PI). MBP and SP-A, -D monomers are homotrimers with an N-terminal collagen region and three CTLDs. Multiple homotrimeric units associate to form supramolecular complexes. MBL deficiency results in an increased susceptibility to a large number of different infections and to inflammatory disease [].
Myelin regulatory factor (Myrf) is a transcription regulator required in vertebrates for expression of central nervous system (CNS) myelin genes such as Mbp and Mog, thereby playing a central role in oligodendrocyte maturation and CNS myelination []. It is also required for the maintenance of expression of myelin genes and the mature oligodendrocytes identity in the adult CNS [, ]. A Caenorhabditis elegans orthologue, pqn-47, may function as a regulator of molting [], while a Dictyostelium orthologue has been described to regulate prestalk differentiation [].This domain is found towards the C terminus of myelin regulatory factor (Myrf) and corresponds to the Intramolecular Chaperone Auto-processing (ICA) domain. It forms a homo-trimer and carries out the auto-cleavage of Myrf releasing the N-terminal homo-trimer from the ER membrane. This allows its entry to the nucleus to function as a homo-trimer transcription factor [].
Bacterial high affinity transport systems are involved in active transport of solutes across the cytoplasmic membrane. Most of the bacterial ABC (ATP-binding cassette) importers are composed of one or two transmembrane permease proteins, one or two nucleotide-binding proteins and a highly specific periplasmic solute-binding protein. In Gram-negative bacteria the solute-binding proteins are dissolved in the periplasm, while in archaea and Gram-positive bacteria, their solute-binding proteins are membrane-anchored lipoproteins [, ].This entry includes maltodextrin binding proteins and cyclodextrin-binding proteins (also known as galactooligosaccharide-binding proteins) from bacteria and archaea.Maltodextrin binding protein (MBP) is the primary component of bacterial high-affinity active transport and chemotaxis []. It is a monomeric protein, with 2 globular domains separated by a 2- or 3-stranded hinge. MBP binds and transports linear oligosaccharides (of up to 7 glucosyl units), as well as 2 cyclic maltodextrins which, although binding tightly, cannot be transported nor initiate a chemotactic response []. It is thought that the hinge region is critical for the correct functioning of MBP, not just in the binding and recognition of sugars,but also in allowing and maintaining the integrity of initiation of both active transport and chemotaxis [].The cyclodextrin-binding protein CYCB (also known as galactooligosaccharide-binding protein GANS) from Bacillus subtilis has been characterised. It is part of the ABC transporter complex GanPQS involved in the uptake of galactooligosaccharides and it has a role in galactan degradation [, ].
