Methionine localization

PelZ is a hydrophilic protein of 420 amino acids with a short hydrophobic sequence at its N-terminal end which has Ae characteristics of the signal sequences of exported proteins. The signal peptide may be 24 amino acids long, which would corroborate wiA the usual length encountered in prokaryotes. The molecular cloning of the pelZ gene in an expression vector pT7-6 allowed for the specific 35S-cysteine-methionine raAo-labelling of PelZ in E. coli K38. We could detect, in crude extracts, the presence of a precursor and a mature form of PelZ. After cell fractionation, Ae mature form of PelZ could be localized in Ae periplasm of E. coli. So PelZ appears to be a protein exported by Ae Sec-dependent system of translocation. 

The Ras proteins are synthesized as biologically inactive, cytosolic precursor proteins. They are then modified by several post-translational processing steps at the carboxyl terminal end and thereby converted into biologically active proteins localized at the plasma membrane. The cysteine of the C-terminal CAAX sequence (C is cysteine, A is generally an aliphatic amino acid, and X is methionine, serine, alanine, or glutamine) is first enzymatically S-farnesylated the AAX part is then cleaved off by a specific protease, and the free C-terminal cysteine is finally converted into a methyl ester (Scheme 1). 

Figure 10.9 Tridimensional structure of GM-CSF.148 The tridimensional structure shows that the four methionine residues present on the molecule have different degrees of solvent exposure. The sulfur atoms are either fully exposed (residues M46 and M79), partially exposed (residue M36), or totally buried (residue M80). Forced oxidation experiments described in the text show that residue M80 is unaffected, whereas local structural constraints make M79 less susceptible to oxidation than predicted by the model. 

Anakinra is a nonglycosylated form of the human IL-1 receptor antagonist (IL-lra). It is produced in a recombinant Escherichia coli expression system and has an additional methionine residue at its amino terminus. In rheumatoid arthritis patients, the amount of naturally occurring IL-lra in the synovial fluid is not sufhcient to counteract the high levels of locally produced IL-1. Anakinra acts as a competitive antagonist of the type 1 IL-1 receptor and decreases the pain and inflammation produced by IL-1. It is administered as a daily subcutaneous injection. 

Advances in ethylene biochemistry and physiology have preceded along a number of fronts. Firstly the biosynthetic pathway from methionine to ethylene has been further clarified and intermediates identified. Secondly some progress has been made in recognising two possible receptor sites which are inhibited by Ag ions and C0 , respectively. Thirdly the localization of ethylene production has been shown to be associated with membranes in studies with protoplasts. 

We routinely clone chemokines using polymerase chain reaction (PCR). The small size of chemokine genes, the frequent addition of N-terminal or C-terminal tags, and the need to localize precisely the initiator methionine codon in bacteria expression systems are all most easily dealt with by amplifying the genes. In this section, it is assumed that the reader has a grasp of basic cloning techniques (18) and is familiar with simple PCR amplification (21). 

KOLOSOVA, N SHERMAN, D., KARLSON, D DUDAREVA, N., Cellular and subcellular localization of S-adenosyl-L- methionine Benzoic acid carboxyl... 

Wang, J., Dudareva, N., Bhakta, S., Raguso, R.A. and Pichersky, E. (1997) Floral scent production in Clarkia breweri (Onagraceae). II. Localization and development modulation of the enzyme S-adenosyl-L-methionine (iso)eugenol O-methyltransferase and phenylpropanoid emission. Plant Physiol., 114, 213-21. 

S-adenosyl-L-methionine (SAMe) is present in nearly all body cells. About 30% of hepatic SAMe is localized in the mitochondria. It is formed from methionine and ATP by SAMe synthetase (G. L. Cantoni, 1952). Transport from the cytosol to the mitochondria takes place via a specific phosphohpid carrier system in the biomembranes. (164, 172) Metabolically, S-adenosyl-L-methionine is an important initial substrate for munerous synthesis pathways (164, 167) ... 

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