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Analysis of the Conserved Cysteine Periodicity of Parameciumbi Variable Surface Antigens
Author(s) -
THAI KWAN Y.,
FORNEY JAMES D.
Publication year - 2000
Publication title -
journal of eukaryotic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 1066-5234
DOI - 10.1111/j.1550-7408.2000.tb00043.x
Subject(s) - biology , cysteine , serine , antigen , alanine , conserved sequence , genetics , mutagenesis , amino acid , peptide sequence , biochemistry , mutation , gene , enzyme , phosphorylation
. The major surface antigens expressed by free‐living and parasitic protozoa commonly contain repeating cysteine motifs. Despite the common occurrence of these repeats their functional significance remains largely unexplored. In this paper we investigate the conserved cysteine repeats within the variable surface antigens of Paramecium tetraurelia. We show that deletion of 2 entire repeating units or portions of repeats near the N‐terminus does not prevent expression of the A51 variable surface antigen. Alteration of a single cysteine to serine residue also has no effect on A51 expression. In contrast, deletions near the C‐terminus of the protein have identified a small segment within the repeats that is required for expression on the surface. The required region contains a number of conserved amino acid residues, yet site‐directed mutagenesis of two residues (serine and threonine to alanine) did not prevent expression. These studies demonstrate the feasibility of using deletion analysis to identify regions critical for the expression of cysteine‐rich surface antigens. The relationship of these results to the structure and expression of cysteine‐rich surface proteins in other protozoa is discussed.