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Made available in DSpace on 2016-10-10T03:52:36Z (GMT). No. of bitstreams: 5 A diverse family of serine proteinase genes expressed in cotton boll weevil.pdf: 926712 bytes, checksum: c6bc5cf59848fa978e2ba79934baf92b (MD5) license_url: 52 bytes, checksum: 3d480ae6c91e310daba2020f8787d6f9 (MD5) license_text: 23851 bytes, checksum: 294cb7010cc40c47642971e073de3dba (MD5) license_rdf: 23892 bytes, checksum: afd5dad10b1d1e6dc10c8c5d25222c7a (MD5) license.txt: 1887 bytes, checksum: 445d1980f282ec865917de35a4c622f6 (MD5) Previous issue date: 2004-06 Fourteen different cDNA fragments encoding serine proteinases were isolated by reverse transcription-PCR from cotton boll weevil (Anthonomus grandis) larvae. A large diversity between the sequences was observed, with a mean pairwise identity of 22% in the amino acid sequence. The cDNAs encompassed 11 trypsin-like sequences classifiable into three families and three chymotrypsin- like sequences belonging to a single family. Using a combination of 5' and 3' RACE, the full-length sequence was obtained for five of the cDNAs, named Agser2, Agser5, Agser6, Agser10 and Agser21. The encoded proteins included amino acid sequence motifs of serine proteinase active sites, conserved cysteine residues, and both zymogen activation and signal peptides. Southern blotting analysis suggested that one or two copies of these serine proteinase genes exist in the A. grandis genome. Northern blotting analysis of Agser2 and Agser5 showed that for both genes, expression is induced upon feeding and is concentrated in the gut of larvae and adult insects. Reverse northern analysis of the 14 cDNA fragments showed that only two trypsin- like and two chymotrypsin-like were expressed at detectable levels. Under the effect of the serine proteinase inhibitors soybean Kunitz trypsin inhibitor and black-eyed pea trypsin/chymotrypsin inhibitor, expression of one of the trypsin-like sequences was upregulated while expression of the two chymotrypsin-like sequences was downregulated. Publicado

Despite the presence of a family of defense proteins, Phaseolus vulgaris can be attacked by bruchid insects resulting in serious damage to stored grains. The two distinct active forms of a-amylase inhibitors, a-AI1 and a-AI2, in P. vulgaris show different specificity toward a-amylases. Zabrotes subfasciatus a-amylase is inhibited by a-AI2 but not by a-AI1. In contrast, porcine a-amylase is inhibited by a-AI1 but not by a-AI2. The objective of this work was to understand the molecular basis of the specificity of two inhibitors in P. vulgaris (a-AI1 and a-AI2) in relation to a-amylases. Mutants of a-AI2 were made and expressed in tobacco plants. The results showed that all the a-AI2 mutant inhibitors lost their activity against the insect a-amylases but none exhibited activity toward the mammalian a-amylase. The replacement of His33 of a-AI2 with the a-AI1-like sequence Ser-Tyr-Asn abolished inhibition of Z. subfasciatus a-amylase. From structural modeling, the conclusion is that the size and complexity of the amylase-inhibitor interface explain why mutation of the N-terminal loop and resultant abolition of Z. subfasciatus a-amylase inhibition are not accompanied by gain of inhibitory activity against porcine a-amylase. Apesar de possuir uma família de proteínas de defesa, o feijão-comum (Phaseolus vulgaris L.) pode ser atacado por insetos bruquídeos causando sérios danos aos grãos armazenados. O P. vulgaris possui duas formas ativas de inibidores de a-amilases, denominadas a-AI1 e a-AI2, que apresentam diferentes especificidades em relação às a-amilases. A a-amilase de Zabrotes subfasciatus é inibida por a-AI2 mas não por a-AI1. Em contraste, a a-amilase pancreática de porco é inibida por a-AI1 mas não é por a-AI2. O objetivo deste trabalho foi entender as bases moleculares da especificidade desses inibidores em relação às a-amilases. Para tanto, foram construídos mutantes do a-AI2, os quais foram expressados em plantas de fumo. Todos os inibidores mutantes deixaram de inibir a a-amilase de inseto sem, contudo, passar a exibir atividade contra a a-amilase de mamífero. Os modelos estruturais explicam por que a substituição de His33 do a-AI2 pela seqüência correspondente do a-AI1 (Ser-Tyr-Asn) aboliu a inibição da a-amilase de Z. subfasciatus. Dos estudos de modelagem molecular pode-se concluir que o tamanho e a complexidade da interface a-amilase-inibidor explicam por que a mutação da alça N-terminal e a quebra da atividade inibitória para a-amilase de Z. subfasciatus não levam ao ganho de atividade inibitória do mutante em relação à a-amilase de porco.

Made available in DSpace on 2016-10-10T03:52:22Z (GMT). No. of bitstreams: 5 Fold recognition analysis of glycosyltransferase families_further members.pdf: 250752 bytes, checksum: b94040056eb24bdd1735946dc3c52f41 (MD5) license_url: 52 bytes, checksum: 2f32edb9c19a57e928372a33fd08dba5 (MD5) license_text: 24259 bytes, checksum: f1f24f769b03eb8f9cd3f53c1090841c (MD5) license_rdf: 24658 bytes, checksum: 9d3847733d3c0b59c7c89a1d40d3d240 (MD5) license.txt: 1887 bytes, checksum: 445d1980f282ec865917de35a4c622f6 (MD5) Previous issue date: 2003 Glycosyltransferases (GTs) are diverse enzymes organized into 65 families. X-ray crystallography and in silico studies have shown many of these to belong to two structural super-families: GT-A and GT-B. Through application of fold recog-nition and iterated sequence searches, we demonstrate that families 60, 62, and 64 may also be grouped into the GT-A fold superfamily. Analysis of conserved acidic residues sug-gests that catalytic sites are better conserved in superfamily GT-B than in GT-A. Although 26% and 29% of GT families may now be confidently placed in superfamilies GT-A and GT-B, respectively, the remaining 45% of families bear no discernible resemblance to either superfamily, which, given the sensitivity of modern fold recognition methods, suggests the existence of novel structural scaffolds associated with GT activity. Furthermore, bioinformatics studies indicate the apparent ease with which mechanismÐinverting or retain-ingÐmay change during evolution. Sim Publicado

Made available in DSpace on 2016-10-10T03:52:35Z (GMT). No. of bitstreams: 5 Use of phage display to select novel cystatins specific for Acanthoscelides obtectus cysteine proteinases.pdf: 362123 bytes, checksum: 0c3cd692f351309b0f34eeec4e90df08 (MD5) license_url: 52 bytes, checksum: 2f32edb9c19a57e928372a33fd08dba5 (MD5) license_text: 24372 bytes, checksum: 94b0a37ff5ec51de8c55507bff4a7ff9 (MD5) license_rdf: 24623 bytes, checksum: 378d22d8fe50e084ee2f354be78cbe62 (MD5) license.txt: 1887 bytes, checksum: 445d1980f282ec865917de35a4c622f6 (MD5) Previous issue date: 2003 Cysteine proteinases from larvae of the common bean weevil, Acanthoscelides obtectus (Coleoptera: Bruchidae), were isolated by ion exchange affinity chromatography on a CM-Cellulose column and used to select mutant cystatins from a library made with the filamentous M13 phage display system. The library contained variant cystatins derived from the nematode Onchocerca volvulus cystatin through mutagenesis of loop 1, which contains the QVVAG motif that is involved in binding to proteinases. After three rounds of selection, the activity of variant cystatins against papain and cysteine proteinases from A. obtectus was assayed by ELISA. Two different variant cystatins (presenting amino acids DVVSA and NTSSA at positions 65–69) bound to A. obtectus cysteine proteinases more tightly than to papain. In contrast, the wild type had similar affinity for A. obtectus proteinases and for papain. These two selected variants cystatins have greater specificity towards A. obtectus cysteine proteinases than the original sequence and could represent good candidate genes for the production of transgenic plants resistant to this insect pest. Sim Publicado

Made available in DSpace on 2016-10-10T03:52:58Z (GMT). No. of bitstreams: 5 B_Helical catalytic domains in glycoside hydrolase families 49.pdf: 500580 bytes, checksum: 5dd05632841dd914add2ffcbe7514a24 (MD5) license_url: 52 bytes, checksum: 3d480ae6c91e310daba2020f8787d6f9 (MD5) license_text: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) license_rdf: 23892 bytes, checksum: afd5dad10b1d1e6dc10c8c5d25222c7a (MD5) license.txt: 1887 bytes, checksum: 445d1980f282ec865917de35a4c622f6 (MD5) Previous issue date: 2002 Abstract X-ray crystallography and bioinformatics studies reveal a tendency for the right-handed L-helix domain architecture to be associated with carbohydrate binding proteins. Here we demonstrate the presence of catalytic L-helix domains in glycoside hydrolase (GH) families 49, 55 and 87 and provide evidence for their sharing a common evolutionary ancestor with two structurally characterized GH families, numbers 28 and 82. This domain assignment helps assign catalytic residues to each family. Further analysis of domain architecture reveals the association of carbohydrate binding modules with catalytic GH L-helices, as well as an unexpected pair of L-helix domains in GH family 55. ) 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies. Publicado

Made available in DSpace on 2016-10-10T03:52:36Z (GMT). No. of bitstreams: 5 The protease inhibitor chagasin of Trypanosoma cruzi adopts an immunoglobulin-type fold and may have.pdf: 192513 bytes, checksum: cbbe914d3620dec4587bcbe72f163bc2 (MD5) license_url: 52 bytes, checksum: 2f32edb9c19a57e928372a33fd08dba5 (MD5) license_text: 24372 bytes, checksum: 94b0a37ff5ec51de8c55507bff4a7ff9 (MD5) license_rdf: 24623 bytes, checksum: 378d22d8fe50e084ee2f354be78cbe62 (MD5) license.txt: 1887 bytes, checksum: 445d1980f282ec865917de35a4c622f6 (MD5) Previous issue date: 2001-08-06 Abstract Chagasin, a protein from Trypanosoma cruzi, is the first member of a new family of cysteine protease inhibitors. Despite its lack of significant sequence identity with known proteins, convincing structural models, using variable light chain templates, could be constructed on the basis of threading results. Experimental support for the final structure came from inhibition data for overlapping oligopeptides spanning the chagasin sequence. Chagasin therefore exemplifies a new protease inhibitor structural class and a new natural use for an immunoglobulin-like domain. Limited sequence resemblance suggests that chagasin may represent the result of a rare horizontal gene transfer from host to parasite. ß 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved. Sim Publicado

Made available in DSpace on 2016-10-10T03:52:29Z (GMT). No. of bitstreams: 5 Purification biochemical characterisation and partial primary structure of a new.pdf: 111978 bytes, checksum: dc0e8fb32cc9808f915fdbc6cf65e6e3 (MD5) license_url: 52 bytes, checksum: 3d480ae6c91e310daba2020f8787d6f9 (MD5) license_text: 23851 bytes, checksum: 294cb7010cc40c47642971e073de3dba (MD5) license_rdf: 23892 bytes, checksum: afd5dad10b1d1e6dc10c8c5d25222c7a (MD5) license.txt: 1887 bytes, checksum: 445d1980f282ec865917de35a4c622f6 (MD5) Previous issue date: 2000 Plant a-amylase inhibitors show great potential as tools to engineer resistance of crop plants against pests. Their possible use is, however, complicated by the observed variations in specificity of enzyme inhibition, even within closely related families of inhibitors. Better understanding of this specificity depends on modelling studies based on ample structural and biochemical information. A new member of the a-amylase inhibitor family of cereal endosperm has been purified from rye using two ionic exchange chromatography steps. It has been characterised by mass spectrometry, inhibition assays and N-terminal protein sequencing. The results show that the inhibitor has a monomer molecular mass of 13 756 Da, is capable of dimerisation and is probably glycosylated. The inhibitor has high homology with the bifunctional a-amylase:trypsin inhibitors from barley and wheat, but much poorer homology with other known inhibitors from rye. Despite the homology with bifunctional inhibitors, this inhibitor does not show activity against mammalian or insect trypsin, although activity against porcine pancreatic, human salivary, Acanthoscelides obtectus and Zabrotes subfasciatus a-amylases was observed. The inhibitor is more effective against insect a-amylases than against mammalian enzymes. It is concluded that rye contains a homologue of the bifunctional a-amylase:trypsin inhibitor family without activity against trypsins. The necessity of exercising caution in assigning function based on sequence comparison is emphasised. Sim Publicado