Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.59 (MIP)
 4,906 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Covalent attachment of fatty acids to proteins may be a means of anchoring cytoplasmic proteins to the plasma membrane. The possibility that lens membrane proteins can be fatty acid acylated was studied by incubating the lenses of young rats with 9,10-3H-palmitate. The distribution of 3H-palmitate among the lens membrane polypeptides separated by electrophoresis was determined by fluorography and by direct measurement of radiolabel in sliced gels. 3H-palmitate was found to be incorporated into membrane polypeptide fractions of approximately 19, 30, and 35 kD; the 30 kD fraction appeared to be most highly labeled. The principal lens membrane protein, the main intrinsic protein (MIP 26), was not labeled. This incorporation appeared to be due to covalent attachment rather than to noncovalent binding, and was temperature dependent, independent of protein synthesis, and resistant to displacement by beta-mercaptoethanol. Whether the acylation is enzymatic or nonenzymatic is unclear. The identity of the acylated polpeptides is unknown.
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PMID:Palmitoylation of ocular lens membrane proteins. 230 34

A number of macrophage-derived mediators have been implicated in the vascular changes of inflammation. We recently reported the isolation of a novel monokine, macrophage inflammatory protein 1 (MIP-1), which causes local inflammatory responses in vivo, and induces superoxide production by neutrophils in vitro. Purified native MIP-1 comprises two peptides with very similar physical characteristics. We report here the resolution of MIP-1 into component peptides by SDS-hydroxylapatite chromatography, and compare the NH2-terminal sequences of the two peptides, now referred to as MIP-1 alpha and MIP-1 beta. A synthetic oligonucleotide probe pool corresponding to the NH2-terminal amino acid sequence of MIP-1 beta was used to isolate a cDNA clone containing its coding sequence. The sequence codes for a 109 amino acid-long polypeptide, of which 69 amino acids correspond to the mature product. Comparison of this MIP-1 beta cDNA with our previously cloned MIP-1 alpha sequence reveals that the MIP-1 peptides, members of a growing family of potential inflammatory mediators, are distinct but highly homologous (58.9% sequence identity) products of different genes.
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PMID:Resolution of the two components of macrophage inflammatory protein 1, and cloning and characterization of one of those components, macrophage inflammatory protein 1 beta. 305 56

We have compared the long-term developmental changes in water-insoluble protein expression by chick lens cells in vitro and in vivo. Crude membrane fractions were prepared by alkali treatment of the urea-insoluble protein fraction, and the proteins analysed by sodium dodecyl sulphate-polyacrylamide (SDS-PAGE) gel electrophoresis. The major component present in the urea-insoluble fraction of chick lens fibres, a 25,000 MW polypeptide (MIP-25K) was more abundant in adult (8 weeks) than day-old post-hatch chick lens fibre masses. MIP-25K was detected in differentiated but not predifferentiated lens cell cultures, and indirect immunofluorescence using anti-bovine MIP antiserum indicated that MIP-25K was localized in the lentoid bodies. Our findings indicate that the urea-insoluble protein profiles of long-term well-differentiated chick lens cell cultures are qualitatively very similar to the profiles of the lens fibres. The data also confirm that the expression of MIP-25K, rather than the expression of water-soluble crystallin protein, is a marker for lens cell differentiation, and confirm earlier reports, which have been disputed, that delta-crystallin (but not alpha-or beta-crystallin) is specifically associated with chick lens fibre membranes.
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PMID:Developmental changes in membrane protein expression by chick lens cells in vivo and in vitro and the detection of main intrinsic polypeptide (MIP). 308 28

In the course of studies on cachectin/TNF being conducted in our laboratory, a novel macrophage product has been detected and characterized. Termed macrophage inflammatory protein or MIP, this protein appears to be an endogenous mediator of the inflammatory events induced by endotoxin. A cDNA cloned probe for this protein has been isolated from a lambda gt10 phage library prepared from poly(A)+ RNA obtained of endotoxin-induced RAW264.7 cells. The sequence codes for a 92 amino acid-long polypeptide, of which 69 amino acids correspond to the mature product. The sequence predicts a molecular weight of 7,889 and structural analysis of the protein indicates a characteristic signal sequence alpha-helix and a hydrophobic core. Sequence data also confirm no sequence similarity to any other protein listed in the Dayhoff data base.
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PMID:Cloning and characterization of a cDNA for murine macrophage inflammatory protein (MIP), a novel monokine with inflammatory and chemokinetic properties. 329 Mar 82

Calcium-binding membrane-bound proteins are present in the vertebrate eye lens. Among these proteins are a distinct group of immunologically related extrinsic EDTA-extractable proteins (EEP) and calmodulin. The EEP proteins contain calcium-binding sites with a total capacity of 25 mol Ca2+ per mol protein. This high calcium-binding capacity of EEP points to a function of these proteins as intracellular calcium store in the lens. However, EEP undergoes a conformational change upon calcium binding, indicating that these proteins may be involved in the regulation of calcium-dependent cellular processes in the lens. One of these processes is the action of communicating lens fiber junctions, which contain EEP as a main protein component. In addition to EEP, another calcium-binding protein in lens, calmodulin, probably functions as mediator of calcium in the regulation of the structure and function of lens junctions. Like other vertebrate calmodulins, lens calmodulin shows a calcium-dependent mobility shift on SDS-polyacrylamide gels and forms immune complexes with antiserum raised against vertebrate calmodulin. Lens calmodulin binds to the junction proteins MIP (main intrinsic protein, MW 26 Kdalton) and a 17.5 Kdalton polypeptide of lens fiber cells in a calcium-independent manner. Via calmodulin the junctions become calcium-sensitive.
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PMID:Calcium-binding lens membrane proteins. 394 61

The in situ distribution of the 26-kdalton Main Intrinsic Polypeptide (MIP or MP 26), a putative gap junction protein in ocular lens fibers, was defined at the electron microscope level using indirect immunoferritin labeling of ultrathin frozen sections of rat lens. MIP was found distributed throughout the plasma membrane of the lens fiber cell, with no apparent distinction between junctional and nonjunctional membrane. MIP was not detectable in the basal or lateral plasma membrane of the lens epithelial cell, including the interepithelial cell gap junctions; nor was MIP detectable in the plasma membrane or gap junctions of the hepatocyte. Previous reports have indicated that the protein composition of the lens fiber cell junction differs from that of the hepatocyte gap junction. The evidence presented here suggests that the composition of the fiber cell junction and plasma membrane is also immunocytochemically distinct from that of its progenitor, the lens epithelial cell.
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PMID:Immunocytochemical localization of the main intrinsic polypeptide (MIP) in ultrathin frozen sections of rat lens. 635 19

Plasma membranes of vertebrate lens fiber cells contain a major intrinsic polypeptide with an apparent molecular weight of 26,000 (MIP26). These plasma membranes are extremely rich in communicating junctions, and it has been suggested that MIP26 is a component of them. MIP26 was purified from cow lenses using preparative SDS gel electrophoresis followed by hydroxylapatite column chromatography. From gel electrophoresis patterns and aggregational properties it was concluded that the MIP26 preparation was homogeneous. The purified MIP26 was used to produce monospecific antibodies in rabbits as assessed by double immunodiffusion and crossed immunoelectrophoresis of purified MIP26 and solubilized lens plasma membranes against the antiserum. Indirect immunocytochemical studies were performed on open and closed lens plasma membrane vesicles by incubation in anti-MIP antiserum followed by ferritin-conjugated goat antirabbit IgG. The conjugate bound unequivocally to lens communicating junctions, indicating that MIP26 is a component of these structures.
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PMID:Immunocytochemical localization of the lens main intrinsic polypeptide (MIP26) in communicating junctions. 703 67

Homopteran insects, and especially Cicadella viridis, display in their digestive tract a specialized epithelial differentiation, the filter chamber (FC) acting as a water-shunting complex. The main intrinsic membrane protein of the FC is a 25,000-Da polypeptide (P25). In this paper we demonstrate that this P25 polypeptide is a member of the MIP family of membrane channel proteins, and that P25 forms homotetramers in the native membranes. Using polymerase chain reaction, a 360-base pair cDNA, named cic, was isolated from RNA of the FC. cic encodes a 119-amino acid polypeptide (CIC) whose homologies with MIP26, AQP1 (CHIP), AQP2, and gamma-TIP are 38, 38, 34, and 20%, respectively. Using a specific antibody raised against a 15-amino acid peptide from the CIC sequence, we concluded that CIC and P25 are identical entities, and hence that P25 belongs to the MIP family. We investigated the quaternary structure of P25 in the membranes of the FC using biophysical analysis of P25 nondenaturing detergent micelles, scanning transmission electron microscopy, and image processing of conventional transmission electron microscopic images. All those different approaches converged to the conclusion that P25 exists as an homotetramer forming a regular two-dimensional array in the membranes.
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PMID:Structural analysis of a MIP family protein from the digestive tract of Cicadella viridis. 754 38

Chemoattractants, including chemokines such as interleukin 8 (IL-8) and related proteins, activate leucocytes via seven-transmembrane-domain G-protein-coupled receptors. A cDNA for a novel receptor of this kind consisting of 327 amino acids was isolated from a human blood monocyte cDNA library. The polypeptide, termed monocyte-derived receptor 15 (MDR15), is an alternative form of the Burkitt's lymphoma receptor 1 (BLR1) encoded by a human Burkitt's lymphoma cDNA [Dobner, Wolf, Emrich and Lipp (1992) Eur. J. Immunol. 22, 2795-2799]. MDR15 and BLR1 cDNAs differ in the 5' region, where the open reading frame of MDR15 is shorter by 45 codons. Southern-blot analysis indicates that the two transcripts for MDR15 and BLR1 are encoded by the same gene. Northern-blot analysis using a probe that hybridizes with both mRNAs demonstrated high-level expression in chronic B-lymphoid leukaemia and non-Hodgkin's lymphoma cells and, to a lesser extent, peripheral blood monocytes and lymphocytes. Reverse transcription-PCR studies with MDR15- and BLR1-specific primers showed similar levels of transcripts for both receptors in RNA that was positive in Northern-blot analysis. MDR15 and BLR1 have high structural similarity to receptors for human IL-8 (about 40% amino acid identity) and other chemokines. However, none of a series of radiolabelled chemokines (IL-8, NAP-2, GRO alpha, PF4, IP10, MCP-1, MCP-2, MCP-3, I-309, RANTES and MIP-1 alpha) and other ligands (C3a and leukotriene B4) bound to Jurkat transfectants that stably expressed either MDR15 or BLR1 mRNA. The fact that MDR15 and BLR1 are expressed on leucocytes and show marked sequence similarity to chemokine receptors suggests the existence of as yet unidentified chemokines. Alternative transcript formation affecting the 5'-terminal part of the coding region may be a way to modify ligand-binding selectivity.
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PMID:Sequence variation of a novel heptahelical leucocyte receptor through alternative transcript formation. 763 92

A vacuole membrane (= tonoplast) subfraction was purified by sedimentation in a discontinuous sucrose gradient (0.6 M/0.3 M) from a crude vacuole fraction isolated from red beetroot storage cells. The vacuole membrane-enriched fraction was injected into the popliteal lymph nodes of rabbits to raise polyclonal antibodies. The resultant serum was tested by indirect immunofluorescence microscopy on cryosections of shoot meristem. Antibodies specifically bound to the tonoplast but not the cytoplasm or the nucleus. By immunogold microscopy of ultrathin frozen sections, the anti-tonoplast antibodies were shown to label the luminal (exoplasmic) surface of the vacuole membrane and vesicular elements of the Golgi complex. Almost all of the antibodies were directed against a polypeptide with an M(r) of 27,000 as determined by Western blotting. A 30,000 M(r) polypeptide was occasionally detected in tonoplast-enriched fractions. It was weakly labeled by the crude immune serum, but not by the serum purified by affinity on the M(r) 27,000 band. The 27 kDa polypeptide which accounted for 10 to 15% of the total membrane proteins was partially characterized. The M(r) 27,000, but not the M(r) 30,000 polypeptide, had Triton X-114 binding properties and was extracted by chloroform:methanol, indicating its high hydrophobicity. On the basis of their partitioning in detergent/aqueous phases it is suggested that the 27 kDa and the 30 kDa polypeptides belong to the tonoplast and to the vacuolar sap, respectively. Neither polypeptide binds to Con A or is sensitive to Endo F digestion, suggesting that they are either unglycosylated polypeptides or glycopeptides with modified oligosaccharides. When separated by SDS-PAGE under non-reducing conditions, the 27 kDa antigen displays a small increase in apparent relative mobility. Its NH2-terminal amino acid sequence shares homology with plant members of the MIP channel family. As suggested by its relative molecular mass, its high hydrophobicity and its NH2-terminal amino acid sequence, the M(r) 27,000 polypeptide from the tonoplast of beetroot may be a new member of the TIP family. It appears to represent a useful specific marker for the vacuole membrane at all developmental stages of the storage parenchyma cells.
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PMID:Antibodies to the tonoplast from the storage parenchyma cells of beetroot recognize a major intrinsic protein related to TIPs. 775 May 15


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