Search results for MTR

Showing 9 results out of 51

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Protein (3 results from a total of 12)

Identifier: R-HSA-3321944
Species: Homo sapiens
Compartment: cytosol
Primary external reference: UniProt: MTR: Q99707
Identifier: R-HSA-3321920
Species: Homo sapiens
Compartment: cytosol
Primary external reference: UniProt: MTR: Q99707
Identifier: R-HSA-3321921
Species: Homo sapiens
Compartment: cytosol
Primary external reference: UniProt: MTR: Q99707

Reaction (3 results from a total of 12)

Identifier: R-HSA-3321918
Species: Homo sapiens
Compartment: cytosol
Methionine synthase (MTR) catalyses the transfer of a methyl group from 5-methyltetrahydrofolate (MTHF) to homocysteine (HCYS) to then form methionine (L-Met). In the first step, MTR mediates the transfer of a methyl group from 5-methyltetrahydrofolate (MTHF) to cob(I)alamin (B12s, bound to the enzyme MTR) to form the cofactor methylcobalamin (MeCbl), the form that activates MTR (Leclerc et al. 1996).

Defects in MTR cause methylcobalamin deficiency type G (cblG, methionine synthase deficiency; MIM:250940), an autosomal recessive inherited disease that causes mental retardation, macrocytic anemia, and homocystinuria. Mutations causing cblG include P1173L, Ile881, H920D, R585*, E1204* and A1204P (Leclerc et al. 1996, Gulati et al. 1996, Watkins et al. 2002).
Identifier: R-HSA-5419264
Species: Homo sapiens
Compartment: mitochondrial matrix, mitochondrial inner membrane
MTRF1L (mtRF1a) binds the stop codons UAA and UAG of the mRNA when they are in the A site of the ribosome (Soleimanpour-Lichaei 2007, Nozaki et al. 2008). (The UGA codon is recognized by the tryptophan tRNA in mitochondrial translation.) ICT1 can also bind standard stop codons in the A-site (inferred from pig mitochondrial ribosomes in Akabane et al. 2014). MTRF1 was also thought to play a role in translation termination by recognizing the unconventional termination codons AGA and AGG (Zhang and Spremulli 1998, Young et al. 2010) but frameshifting is now confirmed in the termination mechanism of these codons (Temperley et al. 2010). Structural features of MTRF1 have been reported suggesting it could recognize an empty A-site (Huynen et al. 2012) or UAA and UAG codons (Lind et al. 2013) however there is no direct experimental data to confirm these last two postulates.
Identifier: R-HSA-3149518
Species: Homo sapiens
Compartment: cytosol
Methionine synthase reductase (MTRR), in a stable complex with methionine synthase (MTR), catalyzes the reduction of cob(II)alamin to methylcobalamin (MeCbl), the cofactor form required for MTR activity. This reductive methylation reaction uses S adenosylmethionine (AdoMet, SAM) as a methyl donor. MTRR requires 1 FMN and 1 FAD per subunit for activity (Wolthers & Scrutton 2007, Wolthers & Scrutton 2009).

An important role for this reaction in the cell is maintenance of the pool of MeCbl-associated MTR. At a low rate, cobalamin bound to MTR is spontaneously oxidized to form cob(II)alamin. When this happens, MTRR this reductive methylation reaction restores cob(II)alamin to MeCbl (Hall et al. 2000).

Defects in MTRR cause methylcobalamin deficiency type E (cblE; MIM:236270) (Wilson et al. 1999). Patients with cblE exhibit megaloblastic anemia and hyperhomocysteinemia. AdoMet is used as a methyl donor in many biological reactions and its demethylation produces homocysteine. Remethylation is carried out by MTR in conjunction with MTRR but in cblE patients, MTR bound cobalamin cannot be reduced by defective MTRR to form a functional enzyme thus homocysteine accumulates. Mutations in MTRR that cause cblE include Leu576del (Leclerc et al. 1998) and S454L (Zavadakova et al. 2005). In terms of frequency, the most common MTRR mutation is a c.903+469C>T mutation which creates a novel splice site deep in an intron and results in inclusion of a 140 bp insertion in MTRR mRNA (Homolova et al. 2010). Wilson et al. showed that a 66A G polymorphism, resulting in an Ile22Met (I22M) substitution, is associated with susceptibility to folate sensitive neural tube defects (FS NTD; MIM:601634) (Wilson et al. 1999b, Doolin et al. 2002). Serum deficiency of vitamin B12 increased the effect.

Complex (3 results from a total of 16)

Identifier: R-HSA-3204327
Species: Homo sapiens
Compartment: cytosol
Identifier: R-HSA-3149530
Species: Homo sapiens
Compartment: cytosol
Identifier: R-HSA-3149551
Species: Homo sapiens
Compartment: cytosol
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