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Molecular characterization of Mycoplasma arthritidis membrane lipoprotein MAA1
L R Washburn1, E J Miller, K E Weaver
1Division of Basic Biomedical Sciences, University of South Dakota, Vermillion, South Dakota 57069-2390, USA. lwashbur@usd.edu
Abstract:
Genes encoding the Mycoplasma arthritidis surface-exposed lipoprotein MAA1 were cloned and sequenced from MAA1-expressing strains 158p10p9 and PG6, from a low-adherence (LA) variant derived from 158p10p9 that expresses a truncated version of MAA1 (MAA1Delta) and from two MAA1-negative strains, 158 and H39. The deduced amino acid sequences of maa1 from 158p10p9 and PG6 predicted, respectively, 86.5- and 86.4-kDa basic, largely hydrophilic lipoproteins with 29-amino-acid signal peptides and predicted cleavage sites for signal peptidase II (Ala-Ala-Ala downward arrowCys). The truncation in the LA variant resulted from a G-->T substitution at nucleotide 695, which created a premature stop codon. This, in turn, generated a predicted 26.6-kDa prolipoprotein (23.6 kDa after processing), consistent with an M(r) of approximately 24,000 calculated for MAA1Delta. Similarly, absence of MAA1 expression in H39 and 158 resulted from C-->A substitutions at nucleotide 208, generating premature stop codons at that site in both strains.
Insights
Mycoplasma arthritidis surface lipoprotein MAA1 gene sequences were analyzed. Genetic mutations causing truncated or absent MAA1 expression were identified in low-adherence and MAA1-negative strains.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Mycoplasma arthritidis is a bacterium that can cause arthritis.
- Surface-exposed lipoproteins play crucial roles in bacterial adhesion and pathogenesis.
- MAA1 is a surface lipoprotein of Mycoplasma arthritidis.
Purpose of the Study:
- To clone and sequence the genes encoding the Mycoplasma arthritidis surface-exposed lipoprotein MAA1.
- To investigate the genetic basis for MAA1 expression in different strains and variants.
Main Methods:
- Gene cloning and sequencing of the maa1 gene from various Mycoplasma arthritidis strains.
- Bioinformatic analysis of deduced amino acid sequences.
- Identification of nucleotide substitutions leading to premature stop codons.
Main Results:
- Sequencing revealed full-length maa1 genes in MAA1-expressing strains (158p10p9 and PG6), predicting basic, hydrophilic lipoproteins.
- A G-to-T substitution in a low-adherence variant (MAA1Delta) created a premature stop codon, resulting in a truncated lipoprotein.
- C-to-A substitutions in MAA1-negative strains (158 and H39) also generated premature stop codons, preventing MAA1 expression.
Conclusions:
- Genetic analysis identified specific mutations responsible for altered MAA1 expression in Mycoplasma arthritidis.
- These mutations, leading to truncated or absent MAA1, correlate with reduced adherence and lack of surface protein expression.
- Understanding these genetic variations is crucial for elucidating the role of MAA1 in M. arthritidis pathogenesis.