CopG, unbound and in complex with 19-bp and 22-bp dsDNAs (1998, 2001)
CopG is a transcriptional repressor responsible for the number control of streptococcal plasmid pMV158, which confers resistance against the antibiotic tetracyclin, within its bacterial host. A homotetramer of this protein, which evinces a ribbon-helix-helix topology, is the minimal functional unit. We solved the native unbound structure (top left), which displayed a cooperative behavior rendering a right-handed superhelix within the crystal (top right). A complex of the protein with a 19-bp dsDNA encompassing the primary recognition sequence (middle) revealed also a continuous superhelix, this time left-handed and made up by DNA-DNA contacts. In contrast, a complex with a 22-bp dsDNA (bottom) showed a right-handed superhelix made up by protein-protein contacts.
Carried out in the laboratories of Miquel Coll and Manuel Espinosa.
Plasmid conjugative coupling protein TrwB (2001)
Transfer of plasmids among bacteria is a major mechanism of antibiotic resistance dissemination. In particular, E. coli plasmid R388 confers resistance against the antibiotics trimethoprim and sulfonamides and it is transferred between bacteria through a type-IV secretion system (T4SS). TrwB is a T4SS coupling protein, encoded by R388 and responsible for linking the nucleoprotein complex (relaxosome), which includes the single-stranded DNA to be transferred during conjugative events, with the transport apparatus. TrwB is a homohexameric basic integral membrane protein of 507 residues. We solved the structure of a soluble variant lacking the first 70 residues, which comprise the transmembrane domain.
Carried out in the laboratories of Miquel Coll and Fernando de la Cruz.
Methicillin resistance transcriptional repressor, MecI, unliganded and bound to 25-bp DNA (2003, 2004)
This dimeric winged helix-turn-helix DNA-binding protein is the transcriptional regulator of a signal-transduction system that regulates methicillin resistance response in MRSA. The dimer is already preformed before DNA binding (bottom; in red) except for the wings, which become reoriented to better bind DNA (bottom; in white; right).
Carried out in the Proteolysis Lab.
Porphyromonas gingivalis HmuY hemophore (2009)
This heme-binding protein is a virulence factor secreted by the major human bacterial odontopathogen to recruit heme, an indispensable nutrient the bacterium is unable to synthesize itself. The structural analysis of the protein in complex with heme unveiled a novel all-β fold mimicking a right hand.
Carried out in the Proteolysis Lab in collaboration with the groups of Jan Potempa and Teresa Olczak.
Staphylococcus aureus (MRSA) methicillin resistance factor MecR2 (2013)
The structure of the long seeked for factor MecR2, which participates in the MecI-MecR1-MecA axis of methicillin resistance in S. aureus, revealed a dimeric structure reminiscent of ROK proteins.
Carried out in the Proteolysis Lab in collaboration with the group of Duarte C. Oliveira.
Porphyromonas gingivalis peptidylarginine deiminase PPAD (2015)
We succeeded in solving the structure of the only bacterial peptidylarginine deiminase described to date. It provides a link between rheumatoid arthritis and periodontal disease.
Carried out in the Proteolysis Lab in collaboration with the group of J. Potempa.