Research Group Members I Principal Investigator: Miquel Pons I Associate Researchers: Pau Bernadó, Jesús García, Juan Carlos Paniagua I Postdoctoral Fellow: Yolanda Pérez I PhD Students: Eric Aragón, Jascha Blobel, Giovanni Cincilla, Tiago Cordeiro, Carles Fernandez de Alba, Arola
ment of this cysteine residue by isoleucine results in an increased affinity for H-NS. However, expression of the mutant in vivo leads to a sharp decrease in viability. This observation points to a direct role of H-NS-bound Hha in the activity of the Hha-H-NS complex (Cordeiro, in preparation). We are currently extending our studies to other proteins that are equally essential or structurally related. Jesus Garcia, in our group, has already identified new relevant interactions involving the N-terminal domain of the ε-subunit of the multi-protein DNA polymerase III complex, with YdgT, a member of the Hha/YmoA/ YdgT family. Also, we are determining the structure of the DNA-binding domain of Ler, a general regulator of virulence, with homology to H-NS in this domain. We have also established new collaborations with the aim to characterise, by means of complementary techniques, the interaction of full-length H-NS with DNA. This research line is a long-term collaboration with Antonio Juarez (University of Barcelona and IBEC).
Regulation of proteins involved in tyrosine phosphorylation signalling Our group has a long standing interest in mammalian low molecular weight tyrosine protein phosphatases (lmwPTPs) and their oligomerisation. Bovine lmwPTP forms enzymatically inactive homodimers at high protein concentration. We hypothesise that phosphatase oligomerisation is a regulatory mechanism of the recovery stage of kinase-mediated signalling events under crowding conditions. In our search for a suitable
Fortian, Oriol Marimón I Master Students: Lidia Ballester, Xiodi Sun I Visitor: Catalina Granados (Colombia)
mimetic of crowding conditions, we have explored the use of arginine-glutamic mixtures and we have characterised bovine lmwPTP oligomerisation using 129 Xe-NMR chemical shifts and 15N-NMR relaxation (Blobel, Schmidl et al, 2007). We have demonstrated that arginine-glutamic mixtures have intriguing emerging properties: enhancement of specific macromolecular interactions and suppression of non-specific contacts. In the presence of arginine-glutamic acid, 129Xe NMR becomes a selective probe of the presence of one of the oligomeric species. We have recently focused our attention on the highly relevant human Src tyrosine kinase, the paradigm of the Src kinase family that includes, in addition to Src, the kinases Fyn, Yes, Fgr, Lyn, Hck, Lck, Blk and Yrc. Src kinase is inactive in the metabolic basal state. The inactive form involves the interaction of a phosphorylated tyrosine with an SH2 domain. By the action of a phosphatase, Src is activated. SAXS data of a mimic of the activated form show that, in contrast to previously reported X-ray data, the active form is not structurally open but is involved in an equilibrium in which 85% of the species are closed (Bernadó et al, 2007b). This result sheds light on the relative stability of the open and closed forms and explains the
S t ruc tural and C omputational Biology Programme 2 0 0 7 Sc i ent i f i c R eport
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