Biomedical subjects

Luiz Augusto Basso

Publications and source records attributed to Luiz Augusto Basso.

25 records · Page 2Linked to original sources

PubMed2003

Structural bioinformatics study of EPSP synthase from Mycobacterium tuberculosis.

The shikimate pathway is an attractive target for herbicides and antimicrobial agent development because it is essential in algae, higher plants, bacteria, and fungi, but absent from mammals. Homologues to enzymes in the shikimate pathway have been identified in the genome sequence of Mycobacterium tuberculosis. Among them, the EPSP synthase was proposed to be present by sequence homology. Accordingly, in order to pave the way for structural and functional efforts towards anti-mycobacterial agent development, here we describe the molecular modeling of 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase isolated from M. tuberculosis that should provide a structural framework on which the design of specific inhibitors may be based on. Significant differences in the relative orientation of the domains in the two models result in "open" and "closed" conformations. The possible relevance of this structural transition in the ligand biding is discussed.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗

PubMed2003

Crystal structure of human PNP complexed with guanine.

Purine nucleoside phosphorylase (PNP) catalyzes the phosphorolysis of the N-ribosidic bonds of purine nucleosides and deoxynucleosides. PNP is a target for inhibitor development aiming at T-cell immune response modulation and has been submitted to extensive structure-based drug design. More recently, the 3-D structure of human PNP has been refined to 2.3A resolution, which allowed a redefinition of the residues involved in the substrate-binding sites and provided a more reliable model for structure-based design of inhibitors. This work reports crystallographic study of the complex of Human PNP:guanine (HsPNP:Gua) solved at 2.7A resolution using synchrotron radiation. Analysis of the structural differences among the HsPNP:Gua complex, PNP apoenzyme, and HsPNP:immucillin-H provides explanation for inhibitor binding, refines the purine-binding site, and can be used for future inhibitor design.

Binding Sites↗

PubMed2003

Structural basis for inhibition of human PNP by immucillin-H.

Purine nucleoside phosphorylase (PNP) catalyzes the phosphorolysis of the N-ribosidic bonds of purine nucleosides and deoxynucleosides. PNP is a target for inhibitor development aiming at T-cell immune response modulation. This work reports on the crystallographic study of the complex of human PNP-immucillin-H (HsPNP-ImmH) solved at 2.6A resolution using synchrotron radiation. Immucillin-H (ImmH) inhibits the growth of malignant T-cell lines in the presence of deoxyguanosine without affecting non-T-cell tumor lines. ImmH inhibits activated normal human T cells after antigenic stimulation in vitro. These biological effects of ImmH suggest that this agent may have utility in the treatment of certain human diseases characterized by abnormal T-cell growth or activation. This is the first structural report of human PNP complexed with immucillin-H. The comparison of the complex HsPNP-ImmH with recent crystallographic structures of human PNP explains the high specificity of immucillin-H for human PNP.

Crystallography, X-Ray↗

PubMed2003

Docking and small angle X-ray scattering studies of purine nucleoside phosphorylase.

Docking simulations have been used to assess protein complexes with some success. Small angle X-ray scattering (SAXS) is a well-established technique to investigate protein spatial configuration. This work describes the integration of geometric docking with SAXS to investigate the quaternary structure of recombinant human purine nucleoside phosphorylase (PNP). This enzyme catalyzes the reversible phosphorolysis of N-ribosidic bonds of purine nucleosides and deoxynucleosides. A genetic deficiency due to mutations in the gene encoding for PNP causes gradual decrease in T-cell immunity. Inappropriate activation of T-cells has been implicated in several clinically relevant human conditions such as transplant rejection, rheumatoid arthritis, lupus, and T-cell lymphomas. PNP is therefore a target for inhibitor development aiming at T-cell immune response modulation and has been submitted to extensive structure-based drug design. The present analysis confirms the trimeric structure observed in the crystal. The potential application of the present procedure to other systems is discussed.

Humans↗

PubMed2003

Crystal structure of human purine nucleoside phosphorylase at 2.3A resolution.

Purine nucleoside phosphorylase (PNP) catalyzes the phosphorolysis of the N-ribosidic bonds of purine nucleosides and deoxynucleosides. In human, PNP is the only route for degradation of deoxyguanosine and genetic deficiency of this enzyme leads to profound T-cell mediated immunosuppression. PNP is therefore a target for inhibitor development aiming at T-cell immune response modulation and its low resolution structure has been used for drug design. Here we report the structure of human PNP solved to 2.3A resolution using synchrotron radiation and cryocrystallographic techniques. This structure allowed a more precise analysis of the active site, generating a more reliable model for substrate binding. The higher resolution data allowed the identification of water molecules in the active site, which suggests binding partners for potential ligands. Furthermore, the present structure may be used in the new structure-based design of PNP inhibitors.

Amino Acid Sequence↗

PubMed2003

Crystal structure of human purine nucleoside phosphorylase complexed with acyclovir.

In human, purine nucleoside phosphorylase (HsPNP) is responsible for degradation of deoxyguanosine and genetic deficiency of this enzyme leads to profound T-cell mediated immunosuppression. PNP is therefore a target for inhibitor development aiming at T-cell immune response modulation and has been submitted to extensive structure-based drug design. This work reports the first crystallographic study of human PNP complexed with acyclovir (HsPNP:Acy). Acyclovir is a potent clinically useful inhibitor of replicant herpes simplex virus that also inhibits human PNP but with a relatively lower inhibitory activity (K(i)=90 microM). Analysis of the structural differences among the HsPNP:Acy complex, PNP apoenzyme, and HsPNP:Immucillin-H provides explanation for inhibitor binding, refines the purine-binding site, and can be used for future inhibitor design.

Acyclovir↗

PubMed2002

Molecular model of shikimate kinase from Mycobacterium tuberculosis.

Tuberculosis (TB) resurged in the late 1980s and now kills approximately 3 million people a year. The reemergence of tuberculosis as a public health threat has created a need to develop new anti-mycobacterial agents. The shikimate pathway is an attractive target for herbicides and anti-microbial agents development because it is essential in algae, higher plants, bacteria, and fungi, but absent from mammals. Homologs to enzymes in the shikimate pathway have been identified in the genome sequence of Mycobacterium tuberculosis. Among them, the shikimate kinase I encoding gene (aroK) was proposed to be present by sequence homology. Accordingly, to pave the way for structural and functional efforts towards anti-mycobacterial agents development, here we describe the molecular modeling of M. tuberculosis shikimate kinase that should provide a structural framework on which the design of specific inhibitors may be based.

Adenosine Diphosphate↗