| Candida albicans,containning three kinds of morphology:single cell sporophyte,multicellular mycelia and pseudomycelium,is a widespread pathogenic fungus.Candida albicans can cause candidiasis,according to the different location of infection,the candidiasis can be divided into the skin candidiasis,oral candidiasis,beriberi and vaginitis,etc.In addition,the deep infection of Candida albicans is fatal and the mortality rate of deep Candida infection is increasing year by year,so Candida albicans has become an important pathogen that threatens human health.Therefore,the study of the biomolecular mechanism of Candida albicans is conducive to understand its pathogenesis better and solve the latent problem caused by infection.IQGAPs is a kind of ubiquitous scaffold protein family in eukaryotes,which are highly conserved.IQGAPs are involved in different cellular processes by interacting with many proteins,including cytokinesis,cell migration,etc.The Iqg1p in Candida albicans is an important member of IQGAPs family.It has four functional regions,CH,IQ motif,GAP and GAPC,and works by binding protein kinase or phosphatase to their respective substrates.In order to further understand the function of Iqg1p,we carried out some regional knockout experiments on the four functional sections of Candida albicans Iqg1p,it is found that Iqg1p N-terminal,including two functional domains of CH and IQ,does not have much effect on cell morphology.While the two functional domains of Iqg1p C-terminal,GAP and GAPC,are of great significance for cell morphology.When the two function section are missing,cells can not split normally and form multinucleated pseudomycelium.What’s more,by the mycelium induction of knockout deficient strains,we find that in different culture medium,each type of segment knockout bacteria has the different ability to form hyphae and the different degree of mycelium defect.Through the protein binding assay in vitro,we find that the GAP functional region of Iqglp has strong interaction with Cdc42p and Rholp.In order to further explore the functional interaction between them,this study constructed the overexpressed mutants of Rholp and Cdc42p by point mutation technology,the Cdc42p 61th glutamine was mutated into leucine to get Cdc42Q61L,and Rho1p 67th glutamine was mutated to leucine to get Rho1Q67L,so that Rho1p and Cdc42p are always in the active state.The results showed that Cdc42Q61L and Rho1Q67L could partially restore the morphological defects of iqg1-shut off,and significantly improved the growth ability of iqgl-shut off under the high temperature of 42℃.These results indicate that Iqglp also interact with Rholp or Cdc42p in function,and further validate the results of protein binding experiments in vitro.What’s more,we try to analyze the spatial structure of Iqglp functional sections by structural biology method.These results are of great help in understanding the functional significance of Iqglp in the biological process of Candida albicans. |
