?Characterization of the Rho protein of the fungus Mucor rouxii?

FIORELLA GALELLO; SILVIA ARGIMON; ELBA PEREYRA; SILVIA ROSSI; SILVIA MORENO

Iguazú, Misiones, Argentina

Congreso; SAIB, XL Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular.; 2004

SAIB

Cell polarity is central to cell function, acting to organise the bochemestry and the structures tha resul in the development of cells with specialized physiology. The Rho family of GTPases, particulary RhoA, have emerged as central coordinators of a remarkable variety of cellular functions including cytoeskeletal organization. RHO1 gene from Mucor rouxii has been cloned, and the deduced aminoacid sequence has highest similarity with S. pombe (88%) and human RhoA (80%). The 3D structure of M. rouxii Rho1p was obteined by molecular modelling through the Swiss-model protein modelling server, using as template the coordinates of crystallized human RhoA. The overall structure is conserved. The expression of Rho1p was confirmed by ADP-ribosylation and cytoinmunofluorescence. Rho1p has a differential expression during germination as was detected by Western-blot and RT-PCR. The M. rouxii RHO1 gene could rescue a S. cerevisiae strain containing a rho1 deletion. Rho1p in S. cerevisiae was identify as the regulatory subunit of b-1,3-glucan synthase. Vegetative M. rouxii cell wall does not have significant amount of glucans, however caspofungin, an antifungal agent which inhibits the synthesis of b-1,3-glucan, has an important effect on morphology and growth. The MEC (minimum effective concentration necessary to observe morphological changes) was 10mg/ml, similar to that in Aspergillus sp and Fusarium spp, suggesting that Rho1p of M. rouxii could regulate b-1,3-glucan synthesis.