Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.24.27 (thermolysin)
 1,894 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Proteolipid protein (PLP) was isolated from white matter of human brain by chloroform/methanol extraction and further purified by chromatography. Performic acid oxidation yielded a product homogeneous in NaDodSO4-polyacrylamide electrophoresis with a molecular mass of 30 kDa. The carboxymethylated PLP was chemically cleaved with cyanogen bromide into four fragments: CNBr I 22-24 kDa, CNBr II 5 kDa, CNBr III 1.4 kDa and CNBr IV 0.7 kDa. HBr/dimethylsulfoxide cleavage at tryptophan residues released four fragments: Trp I 14-16 kDa, Trp II 2.0 kDa, Trp III 5 kDa and Trp IV 7 kDa. Hydrophilic fragments were enriched in 50% formic acid (CNBr II, III, IV and Trp II and III), whereas hydrophobic peptides precipitated from this solvent were CNBr I, Trp I and IV. The fragments were separated by gel filtration with 90% formic acid as solvent and finally purified by gel permeation HPLC (Si 60 and Si 100) for automated liquid and solid-phase Edman degradation. Large fragments were further cleaved with different proteinases (trypsin, V8-proteinase, endoproteinase Lys-C and thermolysin). We used an improved strategy in the sequencing of the human proteolipid protein compared with our approach to the structural elucidation of bovine brain PLP. The amino-acid sequence of human PLP contains 276 residues, the same as found in bovine proteolipid protein. The two sequences proved to be identical. The possible importance of the conservative structure of this integral membrane protein is discussed.
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PMID:Amino-acid sequence of human and bovine brain myelin proteolipid protein (lipophilin) is completely conserved. 404 Dec 37

The chemical cleavage of lipophilin (proteolipid apoprotein) from bovine brain white matter with HBr/dimethyl sulfoxide at the tryptophan residues, under conditions adapted to this hydrophobic protein, releases four fragments with approximate molecular masses 14 kDa (Trp I), 6.8 kDa (Trp IV), 5.2 kDa (Trp III) and 2.1 kDa (Trp II). These fragments have been separated and purified by a combination of solvent distribution, molecular sieve chromatography (Bio-Gel P-150) and high-performance liquid chromatography for automated Edman degradation and combined gas-liquid chromatography/mass spectroscopy. The complete amino acid sequences of Trp II and III and large sequences of Trp I are reported in this communication. The amino acid sequence of Trp IV and the sequences of peptides releasable from lipophilin by proteolytic enzymes (trypsin, thermolysin, subtilisin, chymotrypsin) have been described in previous reports from this laboratory. Despite two small gaps in the complete primary structure of lipophilin from myelin of central nervous system, our sequence data suggest the arrangement of four long hydrophobic sequences (30-40 apolar amino acid residues) within the hydrophobic core of the myelin lipid bilayer, linked by three hydrophilic regions at the aqueous membrane interphase. These features lend lipophilin the properties of a polytopic membrane protein.
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PMID:Lipophilin (proteolipid apoprotein) of brain white matter. Purification and amino acid sequence studies of the four tryptophan fragments. 717 28