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Biomedical subjects

C Baglioni

Publications and source records attributed to C Baglioni.

At least 199 records · Page 11Linked to original sources
PubMed1969

A study of immunoglobulin structure. 3. An estimate of the variability of human light chains.

102 human Bence Jones proteins have been purified by gel filtration, digested with trypsin, and analyzed by peptide mapping. In several cases Bence Jones "fragments", corresponding to the variable half of the corresponding proteins, were observed. The peptide maps of the proteins were compared to establish whether any identical proteins were present in the sample analyzed. No Bence Jones protein showed a peptide map identical to that of any other protein, although remarkable similarities in the peptide maps were observed for some proteins. Two proteins that gave very similar peptide maps were then examined in detail, by purifying and analyzing the tryptic peptides. It was then found that these two proteins differ in amino acid sequence in at least six positions. The probability of not finding two identical sequences by examining a sample extracted from populations of light chains of different sizes has been calculated. This has led to an estimate of the minimal size of the population of light chain sequences in humans. The number of light chain sequences appears to be at least a few thousand. Information on the frequency of Inv and Oz antigenic determinants and on the relative frequency of subtypes of K chains has been obtained. Proteins of KI subtype are found most frequently. The possibility that different subtypes may be predominant in different species is discussed in relation to the evolutionary arguments used in favor of the somatic theories on the origin of variability of immunoglobulin chains.

Amino Acid Sequence↗
PubMed1968

Catabolic origin of a Bence Jones protein fragment.

Gel filtration analysis of the urinary proteins of some patients with myeloma has shown the presence of "fragments" of Bence Jones proteins which correspond to the variable half of these proteins. Experiments have been carried out to establish the origin of a "fragment" observed in a patient who excreted a large amount of this protein. Labeled homologous Bence Jones protein has been injected into this and other control patients. Excretion of labeled "fragment" has been observed in all. Analysis by peptide mapping and radio-autography of this labeled "fragment" isolated from the urine showed that the invariable half of the Bence Jones protein was not excreted; it seemed thus likely that the invariable half was metabolized to small peptides and free amino acids. A labeled Bence Jones protein which was excreted without any accompanying "fragment" was injected into the patient who excreted large amounts of "fragment." No excretion of labeled "fragment" was observed. It was thus concluded that the property of being degraded to "fragment" is characteristic of some "fragile" Bence Jones proteins and is not determined by the patient. Incubation with serum or urine of the "fragile" Bence Jones protein failed to produce any "fragment." "Fragments" of Bence Jones proteins are thus most likely formed during excretion of these proteins through the kidney and are products of the catabolism of Bence Jones proteins.

Autoradiography↗
PubMed1966

A study of immunoglobulin structure. II. The comparison of Bence Jones proteins by peptide mapping.

Urinary proteins of patients with myeloma, prepared by precipitation with ammonium sulphate, have been separated by gel filtration on Sephadex G-100 after reduction and aminoethylation. Many specimens separated into a major peak of Bence Jones protein and into minor peaks of albumin, a protein tentatively identified with heavy chain and a smaller molecular weight protein corresponding to the variable portion of the corresponding Bence Jones protein. The Bence Jones protein purified by gel filtration was analyzed by electrophoresis and by peptide mapping after tryptic digestion. The peptide maps of 24 type K and 20 type L Bence Jones proteins were compared. A set of common peptides was identified in the peptide maps of the Bence Jones proteins of the same type; the common peptides of type K proteins were completely different from the common peptides of type L proteins. The patterns of distinctive peptides was compared; no similarities were found between distinctive peptides of type K and of type L proteins. Some similarities were observed in the distinctive peptides of proteins of the same type. The similarities involved in many cases peptides containing cysteine, whereas similarities in other peptides were limited. This observation suggested that the amino acid sequence around the cysteines of the variable NH(2)-terminal half of the Bence Jones proteins may show less variability than other sequences. A few proteins of the same type differed in all their distinctive peptides, an indication that multiple amino acid differences exist between individual Bence Jones proteins. The genetic mechanisms responsible for the variability in the amino acid sequence of the NH(2)-terminal half of the light chains of immunoglobulins are discussed in view of the results of the comparison by peptide mapping of the Bence Jones proteins.

Amino Acid Sequence↗