Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.2.1.22 (cystathionine beta-synthase)
 965 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigated the effect of truncations on the human muscle chloride channel CLC-1 and studied the functional complementation from partial proteins. Almost complete deletion of the cytoplasmic amino terminus did not affect currents, but truncating the intracellular COOH terminus after Leu720 abolished function. Currents were restored by coexpressing this membrane-embedded part with the lacking cytoplasmic fragment that contains domain D13, the second of the two conserved cystathionine beta-synthase (CBS) motifs present in all eukaryotic CLC proteins. However, if the cut was after Gln597 before the first CBS domain, no functional complementation was seen. Complementation was also obtained with channels "split" between transmembrane domains D7 and D8 or domains D8 and D9, but not when split between D10 and D11. Specificity of currents was tested by inserting point mutations in NH2-terminal (G188A and G230E) or COOH-terminal (K585E) fragments. In contrast to G188A and K585E, split channels did not tolerate the D136G mutation, suggesting that it may impede association from nonlinked fragments. Duplication, but not a lack of domain D8 was tolerated in "split" channels. Membrane domains D9-D12 can insert into the membrane without adding a preceding signal peptide to ensure the extracellular amino terminus of D9. Eventually, we succeeded in reconstituting CLC-1 channels from three separate polypeptides: the amino-terminal part up to D8, D9 through CBS1, and the remainder of the cytoplasmic carboxyl terminus. In summary, several regions of CLC channels behave autonomously regarding membrane insertion and folding and mediate protein-protein interactions strong enough to yield functional channels without a direct covalent link.
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PMID:Reconstitution of functional voltage-gated chloride channels from complementary fragments of CLC-1. 925 64

CBS1 from Magnaporthe grisea is a structural and functional homolog of the cystathionine beta-synthase (CBS) gene from Saccharomyces cerevisiae. Our studies indicated that M. grisea can utilize homocysteine and methionine through a CBS-independent pathway. The results also revealed responses of M. grisea to homocysteine that are reminiscent of human homocystinuria.
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PMID:Molecular characterization of a cystathionine beta-synthase gene, CBS1, in Magnaporthe grisea. 1245 65

TAGKO is a Tn7-based transposition system for genome wide mutagenesis in filamentous fungi. The effects of transposon insertion on the expression of TAGKO alleles were examined in Magnaporthe grisea and Mycosphaerella graminicola. Northern analysis showed that stable, truncated transcripts were expressed in the TAGKO mutants. Mapping of the 3'-ends of TAGKO cDNAs revealed that they all contain Tn7 end sequences, regardless of the transposon orientation. Polyadenylation signals characteristic of eukaryotic genes, preceded by stop codons in all frames, are located in both ends of the bacterial transposon. Thus, TAGKO transcripts are prematurely polyadenylated, and truncated proteins are predicted to be translated in the fungal mutants. Depending on the extent of protein truncation, TAGKO mutations in HPD4 (encoding p-hydroxyphenylpyruvate dioxygenase) resulted in tyrosine sensitivity in the two fungi. Similarly, a particular M.grisea CBS1 (encoding cystathionine beta-synthase) TAGKO cDNA failed to complement cysteine auxotrophy in a yeast CBS mutant. TAGKO, therefore, represents a useful tool for in vivo study of truncated gene products in filamentous fungi.
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PMID:The bacterial transposon Tn7 causes premature polyadenylation of mRNA in eukaryotic organisms: TAGKO mutagenesis in filamentous fungi. 1290 24

Human ClC-1 (skeletal muscle Cl- channel) has a long cytoplasmic C-tail (carboxyl tail), containing two CBS (cystathionine beta-synthase) domains, which is very important for channel function. We have now investigated its significance further, using deletion and alanine-scanning mutagenesis, split channels, GST (glutathione transferase)-pull-down and whole-cell patch-clamping. In tagged split-channel experiments, we have demonstrated strong binding between an N-terminal membrane-resident fragment (terminating mid-C-tail at Ser(720) and containing CBS1) and its complement (containing CBS2). This interaction is not affected by deletion of some sequences, suggested previously to be important, particularly in channel gating. Contact between CBS1 and CBS2, however, may make a major contribution to assembly of functional channels from such co-expressed complements, although the possibility that C-tail fragments could, in addition, bind to other parts of the membrane-resident component has not been eliminated. We now show such an interaction between a membrane-resident component terminating at Ser(720) (but with CBS1 deleted) and a complete C-tail beginning at Leu(598). Channel function is rescued in patch-clamped HEK-293T (human embryonic kidney) cells co-expressing these same fragments. From our own results and those of others, we conclude that the CBS1-CBS2 interaction is not sufficient, in itself, for channel assembly, but rather that this might normally assist in bringing some part of the CBS2/C-tail region into appropriate proximity with the membrane-resident portion of the protein. Previously conflicting and anomalous results can now be explained by an hypothesis that, for split channels to be functional, at least one membrane-resident component must include a plasma membrane trafficking signal between Leu(665) and Lys(680).
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PMID:Analysis of carboxyl tail function in the skeletal muscle Cl- channel hClC-1. 1832 Dec 45