Copyright © 1999 Elsevier Science B.V. All rights reserved.
Molecular cloning and demonstration of an aminopeptidase activity in a filarial nematode glycoprotein*1
Received 23 November 1998;
Abstract
ES-62 is an abundant phosphorylcholine-containing secreted glycoprotein of the filarial nematode Acanthocheilonema viteae. Using an antiserum directed against the parasite molecule, 3 cDNAs of size,
1.5–1.6 kbp were isolated from an A. viteae expression library. Sequence analysis in combination with N-terminal amino acid sequencing of purified ES-62 revealed that each clone contained a full-length cDNA for ES-62 corresponding to 474 amino acid residues but differed in their 5′ and 3′ untranslated regions. Characterisation of the 5′ end of ES-62 mRNA using 5′ rapid amplification of cDNA ends showed that it coded for a signal sequence. Several tryptic peptides were independently sequenced using quadruple-time-of-flight mass spectrometry and used to confirm the cDNA sequence. The mature protein was found to contain three potential N-linked glycosylation sites. Comparison of the derived amino acid sequence of ES-62 with the SwissProt database identified a sequence (between amino acid residues approximately 250 and 350 of mature ES-62) with significant similarity to several bacterial/fungal aminopeptidases. Incubation of ES-62 with leucine-7-amino-4-methylcoumarin as substrate confirmed that ES-62 possessed aminopeptidase activity.
Author Keywords: Acanthocheilonema viteae; Aminopeptidase; cDNA; Filariasis; Secreted product
Abbreviations: Leu-NHMEC, Leucine-7-amido-4-methylcoumarin; MS, Mass spectrometry; PC, Phosphorylcholine
Article Outline
- 1. Introduction
- 2. Materials and methods
- 2.1. Preparation of the A. viteae cDNA library, and screening and isolation of clones
- 2.2. Excision of phagemids
- 2.3. Sequencing of cDNA clones
- 2.4. Preparation of ES-62
- 2.5. N-terminal amino acid sequencing
- 2.6. Preparation of total RNA
- 2.7. Reverse transcription and 5′ rapid amplification of cDNA ends
- 2.8. Polymerase chain reaction
- 2.9. Sequence analysis of amplicons
- 2.10. Quality-time-of-flight mass spectrometry
- 2.11. Western blotting
- 2.12. Measurement of aminopeptidase activity
- 3. Results
- 3.1. Isolation of clones from adult female A. viteae cDNA library using rabbit anti ES-62 serum
- 3.2. Sequencing of the cDNA clones, ES-62A, B, C and D
- 3.3. Q-TOF sequencing of tryptic peptides
- 3.4. Use of 5′ RACE to identify the 5′ end of ES-62 mRNA
- 3.5. Features of the derived amino acid sequence
- 3.6. Features of the nucleotide sequence
- 3.7. Similarities between ES-62 and other proteins
- 3.8. Aminopeptidase activity of ES-62
- 4. Discussion
- Acknowledgements
- References
*1 Note: Nucleotide sequence data reported in this paper are available in the EMBL, GenBank and DDBJ databases under the accession number AF077194.
1 Present address: Creatogen Bioscience GmbH, Augsburg, Germany.
Corresponding author. Tel.: +44-41-548-3725; fax: +44-41-552-6674; email: w.harnett@strath.ac.uk






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