RESUMO
Cellulase genes of Pseudotrichonympha grassii (Hypermastigida: Eucomonymphidae), the symbiotic flagellate in the hindgut of the wood-feeding termite Coptotermes formosanus, were isolated and characterized. The nucleotide sequences of the major cellulase component in the hindgut of C. formosanus were determined based on its N-terminal amino acid sequence. The five isolated nucleotide sequences (PgCBH-homos) had an open reading frame of 1350 bp showing similarity to catalytic domains of glycoside hydrolase family (GHF) 7 members, and primary structure comparison with GHF7 members whose tertiary structures are well-characterized revealed the overall similarity between PgCBH-homo and the catalytic domain of a processive cellulase Cel7A (formerly CBHI) from the aerobic fungus Trichoderma reesei. Functional expression of PgCBH-homos in Escherichia coli, using the carboxymethylcellulose-Congo red assay, demonstrated the actual cellulolytic activity of PgCBH-homo. RT-PCR showed that PgCBH-homos were expressed, from the three flagellates in the hindgut, specifically in P. grassii.
Assuntos
Celulase/genética , Eucariotos/genética , Genes de Protozoários , Isópteros/parasitologia , Sequência de Aminoácidos , Animais , Celulase/química , Celulase/classificação , Escherichia coli/genética , Eucariotos/enzimologia , Eucariotos/fisiologia , Dados de Sequência Molecular , Fases de Leitura Aberta , Filogenia , Alinhamento de Sequência , SimbioseRESUMO
Calcium binding protein 40 (CBP40) is a Ca(2+)-binding protein abundant in the plasmodia of Physarum polycephalum. CBP40 consists four EF-hand domains in the COOH-terminal half and a putative alpha-helix domain in the NH(2)-terminal half. We expressed recombinant proteins of CBP40 in Escherichia coli to investigate its Ca(2+)-binding properties. Recombinant proteins of CBP40 bound 4 mol of Ca(2+) with much higher affinity (pCa(1/2) = 6.5) than that of calmodulin. When residues 1-196 of the alpha-helix domain were deleted, the affinity for Ca(2+) decreased to pCa(1/2) = 4.6. A chimeric calmodulin was generated by conjugating the alpha-helix domain of CBP40 with calmodulin. The affinity of Ca(2+) for the chimeric calmodulin was higher than that for calmodulin, suggesting that the alpha-helix domain is responsible for the high affinity of CBP40 for Ca(2+). CBP40 forms large aggregates reversibly in a Ca(2+)-dependent manner. A mutant protein with a deletion of NH(2)-terminal 32 residues, however, could not aggregate, indicating the importance of these residues for the aggregation. The aggregation occurs above micromolar levels of Ca(2+) concentration, so it may only occur when CBP40 is secreted out of the plasmodial cells.
Assuntos
Proteínas de Ligação ao Cálcio/química , Physarum/química , Proteínas de Protozoários/química , Proteínas Recombinantes de Fusão/química , Animais , Sítios de Ligação/genética , Cálcio/metabolismo , Proteínas de Ligação ao Cálcio/genética , Proteínas de Ligação ao Cálcio/metabolismo , Calmodulina/química , Calmodulina/genética , Calmodulina/metabolismo , Motivos EF Hand/genética , Dados de Sequência Molecular , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/metabolismo , Physarum/metabolismo , Ligação Proteica/genética , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo , Proteínas Recombinantes de Fusão/metabolismoRESUMO
A part of the 3'-flanking region of BP-II gene, which is one of Trimeresurus flavoviridis venom gland phospholopase A2 (PLA2) isozyme genes, has a region homologous to avian chicken repeat 1 (CR1)-element. In the present study, ten CR1-like elements were further identified in T. gramineus venom gland PLA2 isozyme genes, T. flavoviridis PLA2 inhibitor (PLI) genes, and T. flavoviridis and T. gramineus TATA-box binding protein (TBP) genes. Southern blot analysis using a probe for CR1 showed that Crotalinae snake genomes contain a number of CR1-like elements.
Assuntos
Venenos de Crotalídeos/genética , Fosfolipases A/genética , Sequências Repetitivas de Ácido Nucleico , Trimeresurus/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Venenos de Crotalídeos/química , Dados de Sequência Molecular , Fosfolipases A/química , Fosfolipases A2 , Homologia de Sequência de Aminoácidos , Homologia de Sequência do Ácido NucleicoRESUMO
Four acidic phospholipase A2 (PLA2) isozymes named PLA2-I, II, III and IV have previously been isolated from Trimeresurus gramineus (green habu snake) venom and sequenced [Oda et al. (1991) Toxicon 29, 157; Fukagawa et al. (1992) Toxicon 30, 1131; Fukagawa et al. (1993) Toxicon 31, 957]. They contain aspartate-49 which is known to bind Ca2+, essential for catalysis. In the present study, a basic PLA2 named PLA2-V containing lysine-49 was newly isolated from the same snake venom. Its isoelectric point was 9.4 and considerably higher than those (c. 4.5) of PLA2-I-IV. PLA2-V was 1.1% as active as PLA2-I toward egg-yolk emulsion but exhibited strong myotoxicity. The amino acid sequence of PLA2-V was determined by sequencing the S-carboxamidomethylated derivative and its peptide fragments produced by enzymatic (clostripain, chymotrypsin, Achromobacter protease I and Staphylococcus aureus V8 protease) cleavages. PLA2-V consists of 122 amino acid residues and is highly homologous (72-78%) to Lys-49 PLA2s so far isolated from Viperidae snake venoms but less homologous (52%) to PLA2-I. The presence of Asn-28, which is characteristic of Lys-49 PLA2s, was confirmed.
