Abstract
The atypical Gβ-like/RACK1 Gib2 protein promotes cAMP signalling that plays a central role in regulating the virulence of Cryptococcus neoformans. Gib2 contains a seven-bladed β transducin structure and is emerging as a scaffold protein interconnecting signalling pathways through interactions with various protein partners. Here, we present the crystal structure of Gib2 at a 2.2-Å resolution. The structure allows us to analyse the association between Gib2 and the ribosome, as well as to identify the Gib2 amino acid residues involved in ribosome binding. Our studies not only suggest that Gib2 has a role in protein translation but also present Gib2 as a physical link at the crossroads of various regulatory pathways important for the growth and virulence of C. neoformans.
Highlights
The atypical Gb-like/RACK1 Gib[2] protein promotes cAMP signalling that plays a central role in regulating the virulence of Cryptococcus neoformans
The GIB2 deletion strains displayed no reduction in the cAMP levels or apparent defects in melanin and capsule formation, suggesting that they are not directly linked to virulence[14]
Mice infected with the GIB2 deletion strain survived nearly twice as long as those infected with the wild-type strain[14]
Summary
The atypical Gb-like/RACK1 Gib[2] protein promotes cAMP signalling that plays a central role in regulating the virulence of Cryptococcus neoformans. Gib[2] contains a seven-bladed b transducin structure and is emerging as a scaffold protein interconnecting signalling pathways through interactions with various protein partners. Gib[2] was likewise predicted to fold into a seven-bladed b-propeller, similar to that seen in the crystal structure of b transducin[15,16]. Based on the amino acid sequence analysis, Gib[2] is more closely related to RACK1 (receptor for activated kinase C) protein orthologues than to G protein b subunits[13,14]. Saccharomyces cerevisiae) (Fig. 1) suggests that Gib[2] could have functions similar to those of the aforementioned proteins
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