Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.11.18 (MAP)
 7,412 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A yeast gene for a methionine aminopeptidase, one of the central enzymes in protein synthesis, was cloned and sequenced. The DNA sequence encodes a precursor protein containing 387 amino acid residues. The mature protein, whose NH2-terminal sequence was confirmed by Edman degradation, consists of 377 amino acids. The function of the 10-residue sequence at the NH2 terminus, containing 1 serine and 6 threonine residues, remains to be established. In contrast to the structure of the prokaryotic enzyme, the yeast methionine aminopeptidase consists of two functional domains: a unique NH2-terminal domain containing two motifs resembling zinc fingers, which may allow the protein to interact with ribosomes, and a catalytic COOH-terminal domain resembling other prokaryotic methionine aminopeptidases. Furthermore, unlike the case for the prokaryotic gene, the deletion of the yeast MAP1 gene is not lethal, suggesting for the first time that alternative NH2-terminal processing pathway(s) exist for cleaving methionine from nascent polypeptide chains in eukaryotic cells.
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PMID:Molecular cloning, sequencing, deletion, and overexpression of a methionine aminopeptidase gene from Saccharomyces cerevisiae. 156 59

The effect of the antimitotic drug taxol on the association of MAPs (microtubule-associated proteins) with microtubules was investigated. Extensive microtubule assembly occurred in the presence of Taxol at 37 degrees C. at 0 degrees C, and at 37 degrees C in the presence of 0.35 M NaCl, overcoming the inhibition of assembly normally observed under the latter two conditions. At 37 degrees C and at 0 degrees C, complete assembly of both tubulin and the MAPs was observed in the presence of Taxol. However, at elevated ionic strength, only tubulin assembled, forming microtubules devoid of MAPs. The MAPs could also be released from the surface of preformed microtubules by exposure to elevated ionic strength. These properties provided the basis for a rapid new procedure for isolating microtubules and MAPs of high purity from small amounts of biological material. The MAPs could be recovered by exposure of the microtubules to elevated ionic strength and subjected to further analysis. Microtubules and MAPs were prepared from bovine cerebral cortex (gray matter) and from HeLa cells. MAP 1, MAP2, and the tau MAPs, as well as species of Mr = 28,000 and 30,000 (LMW, or low molecular weight, MAPs) and a species of Mr = 70,000 were isolated from gray matter. Species identified as the 210,000 and 125,000 mol wt HeLa MAPs were isolated from HeLa cells. Microtubules were also prepared for the first time from white matter. All of the MAPs identified in gray matter preparations were identified in white matter, but the amounts of individual MAP species differed. The most striking difference in the two preparations was a fivefold lower level of MAP 2 relative to tubulin in white matter than in gray. The high molecular weigh MAP, MAP1, was present in equal ratio to tubulin in white and gray matter. These results indicate that MAP 1 and MAP2, as well as other MAP species, may have a different cellular or subcellular distribution.
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PMID:A taxol-dependent procedure for the isolation of microtubules and microtubule-associated proteins (MAPs). 612 Sep 44

With a rabbit antiserum specific for high molecular weight microtubule-associated proteins (HMW/MAPs: MAP1 and MAP2), centrosomes in interphase and mitotic HeLa cells were visualized by indirect immunofluorescence. Pre-immune serum did not stain a similar organelle. Microtubules were observed to originate from the centrosomes, demonstrating their microtubule organizing (MTOC) function. The MTOC antigen(s) to which the anti-HMW/MAP antiserum reacted was resistant to Colcemid, Triton-X-100, Nonidet P-40 and Brij 35. Immunofluorescence localization of the MTOCs was blocked by pre-incubation of the antiserum with a MAP1--MAP2 preparation but not with tubulin, actin, or a 58 K intermediate filament protein.
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PMID:Localization of high molecular weight microtubule-associated proteins (MAP1 and MAP2) in a HeLa microtubule-organizing centre. 676 Oct 77

Limited proteolysis of intact yeast methionine aminopeptidase (MAP1) with trypsin releases a 34 kDa fragment whose NH2-terminal sequence begins at Asp70, immediately following Lys69. These results suggest that yeast MAP may have a two-domain structure consisting of an NH2-terminal zinc finger domain and a C-terminal catalytic domain. To test this, a mutant MAP lacking residues 2-69 was generated, overexpressed, purified and analyzed. Metal ion analyses indicate that 1 mol of wild-type yeast MAP contains 2 mol of zinc ions and at least 1 mol of cobalt ion, whereas 1 mol of the truncated MAP lacking the putative zinc fingers contains only a trace amount of zinc ions but still contains one mole of cobalt ion. These results suggest that the two zinc ions observed in the native yeast MAP are located at the Cys/His rich region and the cobalt ion is located in the catalytic domain. The kcat and Km values of the purified truncated MAP are similar to those of the wild-type MAP when measured with peptide substrates in vitro and it appears to be as active as the wild-type MAP in vivo. However, the truncated MAP is significantly less effective in rescuing the slow growth phenotype of map mutant than the wild-type MAP. These findings suggest that the zinc fingers are essential for normal MAP function in vivo, even though the in vitro enzyme assays indicate that they are not involved in catalysis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Evidence that two zinc fingers in the methionine aminopeptidase from Saccharomyces cerevisiae are important for normal growth. 786 96

Microtubule proteins were isolated by a temperature-dependent assembly-disassembly method from brain tissue of for cold-temperature fish; one fresh water fish (Oncorhynchus mykiss), and three marine fish (Labrus berggylta, Zoarces viviparus and Gadus morhua). The alpha-tubulins from all four fish species were acetylated. The alpha-tubulins from the marine fish were composed of a mixture of tyrosinated and detyrosinated tubulin, while the fresh water fish tubulin only reacted with an antibody against detyrosinated tubulin. The isolated microtubules had a similar MAP composition. A 400 kD protein and a MAP2-like protein were found, but MAP1 was missing. All microtubules disassembled upon cooling to 0 degrees C. In spite of these common characteristics, the assembly of microtubules from Labrus berggylta was inhibited by colchicine and calcium, in contrast to the assembly of microtubules from Oncorhynchus mykiss and Zoarces viviparus. For the latter, colchicine was not completely inhibitory even at a concentration as high as 1 mM, and calcium induced the formation of both loosely and densely coiled ribbons. The effects of calcium and colchicine on microtubules from Oncorhynchus mykiss and Zoarces viviparus were modulated by either fish or cow MAPs, indicating that the effects are due to intrinsic properties of the fish tubulins and not the MAPs. In view of these findings, our results suggest that there is no correlation between colchicine sensitivity, inability of calcium to inhibit microtubule assembly, and acetylation and detyrosination.
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PMID:Different stability of posttranslationally modified brain microtubules isolated from cold-temperate fish. 802 93

We previously characterized a methionine aminopeptidase (EC 3.4.11.18; Met-AP1; also called peptidase M) in Saccharomyces cerevisiae, which differs from its prokaryotic homologues in that it (i) contains an N-terminal zinc-finger domain and (ii) does not produce lethality when disrupted, although it does slow growth dramatically; it is encoded by a gene called MAP1. Here we describe a second methionine aminopeptidase (Met-AP2) in S. cerevisiae, encoded by MAP2, which was cloned as a suppressor of the slow-growth phenotype of the map1 null strain. The DNA sequence of MAP2 encodes a protein of 421 amino acids that shows 22% identity with the sequence of yeast Met-AP1. Surprisingly, comparison with sequences in the GenBank data base showed that the product of MAP2 has even greater homology (55% identity) with rat p67, which was characterized as an initiation factor 2-associated protein but not yet shown to have Met-AP activity. Transformants of map1 null cells expressing MAP2 in a high-copy-number plasmid contained 3- to 12-fold increases in Met-AP activity on different peptide substrates. The epitope-tagged suppressor gene product was purified by immunoaffinity chromatography and shown to contain Met-AP activity. To evaluate the physiological significance of Met-AP2, the MAP2 gene was deleted from wild-type and map1 null yeast strains. The map2 null strain, like the map1 null strain, is viable but with a slower growth rate. The map1, map2 double-null strains are nonviable. Thus, removal of N-terminal methionine is an essential function in yeast, as in prokaryotes, but yeast require two methionine aminopeptidases to provide the essential function which can only be partially provided by Met-AP1 or Met-AP2 alone.
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PMID:Amino-terminal protein processing in Saccharomyces cerevisiae is an essential function that requires two distinct methionine aminopeptidases. 861

Lipopolysaccharide (LPS) is a main trigger substance for the development of septic shock and multiple organ failure. We showed by turbidity measurements that LPS inhibits microtubule formation in a pH-dependent manner. Inhibition was found to be not only due to sequestration of MAP2 by LPS, but also of MAP1 and tau MAPs, indicating that LPS is able to react with a broad variety of MAPs. LPS-induced inhibition of microtubule formation could be compensated by additional tau or by addition of taxol. Dot blots revealed that LPS binds directly to tau, but seems not to bind to tubulin. As tau is expressed in various tissue types involved in multiorgan failure, it might be regarded as a further target for LPS action. In contrast, kinesin-dependent microtubule gliding was not affected by LPS. The toxin neither blocked the cargo (vesicle) nor the microtubule binding site of kinesin, suggesting a certain specificity of LPS-MAP interaction.
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PMID:Microtubule formation and kinesin-driven microtubule gliding in vitro in the presence of lipopolysaccharide. 1062 22

The effects of two toxins, sodium cyanide (NaCN) and ionomycin (IM), on neuronal viability and on the expression of the microtubule-associated proteins MAP1, MAP2, and tau were studied in isolated chick cortical neurons. Cytotoxic hypoxia due to NaCN treatment was performed to mimic acute neuronal damage, whereas long-term IM treatment was used as a model for chronic neuronal impairment. After 5 days in vitro, a cytotoxic lesion was induced either by addition of NaCN (0.01-10 mM) or IM (0.01-10 microM). The NaCN solution was aspirated after 30 min and cells were allowed to regenerate for 6 h, 24 h, 48 h, or 72 h; whereas the permanent IM lesions were left undisturbed during the same periods of time. Neuronal viability was assessed by MTT assay. The abundance of MAP1, MAP2, and tau was evaluated by immunoblotting and, for MAP2, by immunohistochemistry also. Results showed that NaCN and IM lesions dose-dependently decreased viability. Irreversible cell damage occurred after impairment with 10 mM NaCN and 1 microm or 10 microm IM, while neurons lesioned with lower concentrations regenerated partially or adapted to the toxic environment. However, the same level of viability as of untreated cells was never reached. Furthermore abundance of MAPs was changed after both lesions. But while after extended recovery from NaCN lesion protein expression was normalizing (MAP2) or at least still detectable (MAP1A, tau), the consequences of a permanent IM lesion were more severe, since neurons were not able to maintain or even restore their MAP expression. Immunohistochemical experiments for MAP2 revealed that, compared with controls, NaCN and, to a much higher extent, IM treatment resulted in a loss of immunoreactivity in neurites due to progressing cell death.
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PMID:Effects of NaCN and ionomycin on neuronal viability and on the abundance of microtubule-associated proteins MAP1, MAP2, and tau in isolated chick cortical neurons. 1107 14

Alzheimer disease (AD) and related tauopathies are all characterized histopathologically by neurofibrillary degeneration. The neurofibrillary changes, whether of paired helical filaments (PHF), twisted ribbons or straight filaments (SF) are made up of abnormally hyperphosphorylated tau. Unlike normal tau which promotes assembly and maintains structure of microtubules, the abnormal tau not only lacks these functions but also sequesters normal tau, MAP1 and MAP2, and causes disassembly of microtubules. This toxic behavior of the abnormal tau is solely due to its hyperphosphorylation because dephosphorylation restores it into a normal-like protein. The abnormal hyperphosphorylation also promotes the self-assembly of tau into PHF/SF. The state of phosphorylation of a phosphoprotein is the function of the activities of protein kinases and as well as of protein phosphatases that regulate the level of phosphorylation. A cause of the abnormal hyperphosphorylation in AD brain is a decrease in the activity of protein phosphatase (PP)-2A, a major regulator of the phosphorylation of tau. A decrease in PP-2A activity results in the abnormal hyperphosphorylation of tau not only by decreased dephosphorylation of tau but also by stimulating the activities of tau kinases like CaMKII, PKA and MAP kinases which are regulated by PP-2A. Thus, the abnormal hyperphosphorylation can be inhibited both by inhibition of the activity/s of a tau protein kinase and as well as by restoration of the activity/s of a tau protein phosphatase. The development of drugs that inhibit neurofibrillary degeneration is a very promising and feasible therapeutic approach to inhibit the progression of AD and related tauopathies.
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PMID:Pharmacological approaches of neurofibrillary degeneration. 1597 99

Understanding bacterial genetic diversity is crucial to comprehend pathogenesis. Ehrlichia ruminantium (E. ruminantium), a tick-transmitted intracellular bacterial pathogen, causes heartwater disease in ruminants. This model rickettsia, whose genome has been recently sequenced, is restricted to neutrophils and reticulo-endothelial cells of its mammalian host and to the midgut and salivary glands of its vector tick. E. ruminantium harbors a multigene family encoding for 16 outer membrane proteins including MAP1, a major antigenic protein. All the 16 map paralogs are expressed in bovine endothelial cells and some are specifically translated in the tick or in the mammalian host. In this study, we carried out phylogenetic analyses of E. ruminantium using sequences of 6 MAP proteins, MAP1, MAP1-2, MAP1-6, MAP1-5, MAP1+1 and MAP1-14, localized either in the center or at the borders of the map genes cluster. We show that (i) map1 gene is a good tool to characterize the genetic diversity among Africa, Caribbean islands and Madagascar strains including new emerging isolates of E. ruminantium; (ii) the different map paralogs define different genotypes showing divergent evolution; (iii) there is no correlation between all MAP genotypes and the geographic origins of the strains; (iv) The genetic diversity revealed by MAP proteins is conserved whatever is the scale of strains sampling (village, region, continent) and thus was not related to the different timing of strains introduction, i.e. continuous introduction of strains versus punctual introduction (Africa versus Caribbean islands). These results provide therefore a significant advance towards the management of E. ruminantium diversity. The differential evolution of these paralogs suggests specific roles of these proteins in host-vector-pathogen interactions that could be crucial for developing broad-spectrum vaccines.
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PMID:Mining the genetic diversity of Ehrlichia ruminantium using map genes family. 1981 29


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