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R Monaco

Publications and source records attributed to R Monaco.

50 records · Page 3Linked to original sources
PubMed1994

Conformational effects of environmentally induced, cancer-related mutations in the p53 protein.

The tumor suppressor gene p53 has been identified as the most frequent target of genetic alterations in human cancers. A considerable number of environmentally induced, cancer-related p53 mutations in human tumors have been found in a highly conserved proline-rich sequence of the p53 protein encompassed by amino acid residues 147-158. Using conformational energy analysis based on ECEPP (Empirical Conformational Energy for Peptides Program), we have determined the low-energy three-dimensional structures for this dodecapeptide sequence for the human wild-type p53 protein and three environmentally induced, cancer-related mutant p53 proteins with His-151, Ser-152, and Val-154, respectively. The results suggest that the wild-type sequence adopts a well-defined low-energy conformation and that the mutant peptides adopt well-defined conformations that are distinctly different from the conformation of the wild-type peptide. These results are consistent with experimental conformational studies demonstrating altered detectability of antigenic epitopes in wild-type and mutant p53 proteins. These results suggest that the oncogenic effects of these environmentally induced, cancer-related, mutant p53 proteins may be mediated by distinct local conformational changes in the protein.

Amino Acid Sequence↗
PubMed1994

Conformation of the transmembrane domain of the epidermal growth factor receptor.

The transmembrane domain of growth factor receptors, such as the epidermal growth factor receptor (EGFR) and the related c-erbB-2/neu oncogene protein, has been implicated in the process of receptor dimerization and mitogenic signal transduction, and hence in cellular transformation and oncogenesis. Amino acid substitutions in the transmembrane domain of the c-erbB-2/neu protein that cause a transforming effect may exert this effect through a conformational change from a bend conformation to an alpha-helical structure in this region of the protein, but similar amino acid substitutions at homologous positions in the transmembrane domain of the EGFR (e.g., Val-->Glu at position 627) fail to have a transforming effect. To examine whether this failure may be due to structural effects, we have used conformational energy analysis to determine the preferred three-dimensional structures for the nonapeptide sequence of the transmembrane domain of the EGFR from residues 623-631 with Val or Glu at position 627. The global minimum energy conformations of both nonapeptides were found to be non-alpha-helical with bends at positions 624-625 and 627-628. The failure of the Val-->Glu substitution to produce a conformational change to an alpha-helix in this region may be responsible for its lack of transforming effect. However, the presence of higher energy alpha-helical conformations for the nonapeptide from the normal EGFR may provide an explanation for the presence of a transforming effect from overexpression of the EGFR.

Amino Acid Sequence↗
PubMed1994

Comparison of the low energy conformations of an oncogenic and a non-oncogenic p21 protein, neither of which binds GTP or GDP.

Oncogenic p21 protein, encoded by the ras-oncogene, that causes malignant transformation of normal cells and many human tumors, is almost identical in sequence to its normal protooncogene-encoded counterpart protein, except for the substitution of arbitrary amino acids for the normally occurring amino acids at critical positions such as Gly 12 and Gln 61. Since p21 is normally activated by the binding of GTP in place of GDP, it has been postulated that oncogenic forms must retain bound GTP for prolonged time periods. However, two multiply substituted p21 proteins have been cloned, neither of which binds GDP or GTP. One of these mutant proteins with Val for Gly 10, Arg for Gly 12, and Thr for Ala 59 causes cell transformation, while the other, similar protein with Gly 10, Arg 12, Val for Gly 13 and Thr 59 does not transform cells. To define the critical conformational changes that occur in the p21 protein that cause it to become oncogenic, we have calculated the low energy conformations of the two multiply substituted mutant p21 proteins using a new adaptation of the electrostatically driven Monte Carlo (EDMC) technique, based on the program ECEPP. We have used this method to explore the conformational space available to both proteins and to compute the average structures for both using statistical mechanical averaging. Comparison of the average structures allows us to detect the major differences in conformation between the two proteins. Starting structures for each protein were calculated using the recently deposited x-ray crystal coordinates for the p21 protein, that was energy-refined using ECEPP, and then perturbed using the EDMC method to compute its average structure. The specific amino acid substitutions for both proteins were then generated into the lowest energy structure generated by this procedure, subjected to energy minimization and then to full EDMC perturbations. We find that both mutant proteins exhibit major differences in conformation in specific regions, viz., residues 35-47, 55-78, 81-93, 96-110, 115-126, and 123-134, compared with the EDMC-refined x-ray structure of the wild-type protein. These regions have been found to be the most flexible in the p21 protein bound to GDP from prior molecular dynamics calculations (Dykes et al., 1993). Comparison of the EDMC-average structure of the transforming mutant with that of the nontransforming mutant reveals major structural differences at residues 10-16, 32-40, and 60-68. These structural differences appear to be the ones that are critical in activation of the p21 protein.(ABSTRACT TRUNCATED AT 400 WORDS)

Crystallography, X-Ray↗
PubMed1992

[A Morgagni-Larrey hernia. A case report].

The paper reports a case of Morgagni-Larrey hernia observed by the authors. The etiopathogenesis is described and the importance of surgery is underlined even in asymptomatic cases in order to ensure a benign postoperative outcome.

Female↗
PubMed1981

[Correlation between hyperamylasemia and acute pancreatitis].

It is often difficult to differentiate acute pancreatitis (A.P.) from some other acute abdominal diseases, when there is an elevated serum amylase. In contrast, the renal clearance of amylase, expressed as a percentage of creatinine clearance, can separate patients with A.P. from patients with acute colecistitis, common duct stone without pancreatitis, hyperamylasemia after biliary surgery, acute peptic ulcer and acute salivary diseases.

Acute Disease↗
PubMedDate not supplied

[Agnathia, microstomia, synotia].

The authors describe a case of plurimalformative syndrome, characterized by agnathia, microstomia, synotia and by cardiac and pulmonary maldevelopment. The case peculiarity consist in the rarity of this malformative occurrence; moreover, the authors underline the occurrence of familiarity with Seckel's Syndrome.

Abnormalities, Multiple↗
PubMedDate not supplied

[Chronic obstructive bronchopneumopathy and ectodermal dysplasia].

A boy, 5 year aged, admitted in intensive therapy room because affected by respiratory insufficiency, is reported. Recurrent lower respiratory tract infections and three surgical operation in the lacrimal ducts were present in the anamnesis. Clinical and radiologic features of chronic obstructive pneumonia were present. Hypotrichosis, onychodystrophy, microdontia, associated with absence of muciparous glands and greatly reduced muciparous cells of respiratory tract, were other findings.

Bronchi↗