Dataset Information

Mechanisms involved in the functional divergence of duplicated GroEL chaperonins in Myxococcus xanthus DK1622.

ABSTRACT: The gene encoding the GroEL chaperonin is duplicated in nearly 30% of bacterial genomes; and although duplicated groEL genes have been comprehensively determined to have distinct physiological functions in different species, the mechanisms involved have not been characterized to date. Myxococcus xanthus DK1622 has two copies of the groEL gene, each of which can be deleted without affecting cell viability; however, the deletion of either gene does result in distinct defects in the cellular heat-shock response, predation, and development. In this study, we show that, from the expression levels of different groELs, the distinct functions of groEL1 and groEL2 in predation and development are probably the result of the substrate selectivity of the paralogous GroEL chaperonins, whereas the lethal effect of heat shock due to the deletion of groEL1 is caused by a decrease in the total groEL expression level. Following a bioinformatics analysis of the composition characteristics of GroELs from different bacteria, we performed region-swapping assays in M. xanthus, demonstrating that the differences in the apical and the C-terminal equatorial regions determine the substrate specificity of the two GroELs. Site-directed mutagenesis experiments indicated that the GGM repeat sequence at the C-terminus of GroEL1 plays an important role in functional divergence. Divergent functions of duplicated GroELs, which have similar patterns of variation in different bacterial species, have thus evolved mainly via alteration of the apical and the C-terminal equatorial regions. We identified the specific substrates of strain DK1622's GroEL1 and GroEL2 using immunoprecipitation and mass spectrometry techniques. Although 68 proteins bound to both GroEL1 and GroEL2, 83 and 46 proteins bound exclusively to GroEL1 or GroEL2, respectively. The GroEL-specific substrates exhibited distinct molecular sizes and secondary structures, providing an encouraging indication for GroEL evolution for functional divergence.

SUBMITTER: Wang Y

PROVIDER: S-EPMC3578752 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Mechanisms involved in the functional divergence of duplicated GroEL chaperonins in Myxococcus xanthus DK1622.

Wang Yan Y Zhang Wen-yan WY Zhang Zheng Z Li Jian J Li Zhi-feng ZF Tan Zai-gao ZG Zhang Tian-tian TT Wu Zhi-hong ZH Liu Hong H Li Yue-zhong YZ

PLoS genetics 20130221 2

The gene encoding the GroEL chaperonin is duplicated in nearly 30% of bacterial genomes; and although duplicated groEL genes have been comprehensively determined to have distinct physiological functions in different species, the mechanisms involved have not been characterized to date. Myxococcus xanthus DK1622 has two copies of the groEL gene, each of which can be deleted without affecting cell viability; however, the deletion of either gene does result in distinct defects in the cellular heat-s ...[more]

PMID: 23437010

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Project description:Due to the high similarity in their requirements for space and food, close bacterial relatives may be each other's strongest competitors. Close bacterial relatives often form visible boundaries to separate their swarming colonies, a phenomenon termed colony-merger incompatibility. While bacterial species are known to have many incompatible strains, it is largely unclear which traits lead to multiple incompatibilities and the interactions between multiple incompatible siblings. To investigate the competitive interactions of closely related incompatible strains, we mutated Myxococcus xanthus DK1622, a predatory bacterium with complex social behavior. From 3392 random transposon mutations, we obtained 11 self-identification (SI) deficient mutants that formed unmerged colony boundaries with the ancestral strain. The mutations were at nine loci with unknown functions and formed nine independent SI mutants. Compared with their ancestral strain, most of the SI mutants showed reduced growth, swarming and development abilities, but some remained unchanged from their monocultures. When pairwise mixed with their ancestral strain for co-cultivation, these mutants exhibited improved, reduced or unchanged competitive abilities compared with the ancestral strain. The sporulation efficiencies were affected by the DK1622 partner, ranging from almost complete inhibition to 360% stimulation. The differences in competitive growth between the SI mutants and DK1622 were highly correlated with the differences in their sporulation efficiencies. However, the competitive efficiencies of the mutants in mixture were inconsistent with their growth or sporulation abilities in monocultures. We propose that the colony-merger incompatibility in M. xanthus is associated with multiple independent genetic loci, and the incompatible strains hold competitive interaction abilities, which probably determine the complex relationships between multiple incompatible M. xanthus strains and their co-existence strategies.

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Dataset Information

Mechanisms involved in the functional divergence of duplicated GroEL chaperonins in Myxococcus xanthus DK1622.

Publications

Mechanisms involved in the functional divergence of duplicated GroEL chaperonins in Myxococcus xanthus DK1622.

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