[Description of an ultra-micro method for the sequential analysis of peptides]

Electrophoretic mobility of N- and C-terminal monoferric fragments of bovine transferrin phenotypes AA, D1D1, D2D2, and EE, and N-terminal amino acid sequences

Iron-saturated bovine transferrins A, D1, D2 and E were cleaved by trypsin yielding monoferric fragments. The N-terminal fragments (F) of transferrins A and D2 had identical mobility in cellulose acetate electrophoresis, that of transferrin D1 a slower mobility, and that of E a still slower mobility. The C-terminal fragments (S) gave multiple bands which were essentially identical in the case of transferrins A, D1, and E, but of slower mobility in the case of transferrin D2. All four variants had identical N-terminal amino acid sequences. The electrophoretic mobility of the C-terminal fragments was reduced by neuraminidase treatment, but the N-terminal fragments were unaffected. The four transferrin variants therefore appear to be made up from three electrophoretically distinguishable N-terminal halves and two C-terminal halves. The feature responsible for the electrophoretic double banding of homozygous bovine asialotransferrins is consistently associated with the C-terminal half of the molecule.

The VkVI subgroup of rabbit light chains: complete amino acid sequence of a third variable region (K29-213)

The amino acid sequence of the variable region of a rabbit anti-streptococcal A-variant antibody light chain was determined. By using a combination of different cleavage methods, the sequence was established. Large peptides were sequenced in an extensively modified Beckman sequentor. Light chain K29-213 belongs to a rare subgroup (kVI). Several of these light chains of antibodies with different specificities have been totally or partially sequenced. Comparison of these light chains reveals at least four germ-line-encoded variants within this subgroup.

Variable-region subgroup and specificity of cold agglutinins

The variable-region subgroup determined by amino acid sequence analysis of heavy and light chains of two monoclonal cold agglutinins with the new anti-Gd specificity is reported. Both proteins belong to the VHIII subgroup of heavy chains; one light chain falls into the V kappaI subgroup, the other has a blocked N-terminus which so far has not been observed in human kappa chains. The comparison of anti-Gd with anti-I/-i or anti-Pr cold agglutinins indicates that anti-Gd differs from other cold agglutinins with respect to variable-region subgroup. The data extend previous findings on the restriction of certain antibodies to distinct variable-region subgroups.

[Preparation and partial physico-chemical characterization of sheep-serum transferrin]

Sheep-serum transferrin shows marked polymorphism and more than 20 alleles have been identified although only 4 or 5 of these have a frequency higher than 1%. Each of the alleles has two bands in starch-gel electrophoresis, corresponding to a major and a minor fraciton. This paper describes the isolation and partial characterisation of the two fractions from the transferrin of sheep homozygous for Tf B. The purification consisted of: (a) precipitation by ammonium sulphate, (b) chromatography on CM-cellulose and, finally (c) chromatography on DEAE-Dephadex. The purification procedure had no effect on the electrophoretic mobility of the two fractions and they appeared homogeneous by starch-gel and polyamide-gel electrophoresis and by immuno-electrophoresis. The amino-acid compositions of both fractions were very similar and the sequences of the first eight amino-acid residues: Ser-Pro-Glu-Lys-Thr-Val-Arg-Trp- were identical for both bands. These results, and the fact that the two fractions are found in all genetic variants and always have the same relative mobility strongly suggest that the differences do not lie in the polypeptide chain. From the results of hydrolysis by neuraminidase and assay of sialic acid, the major and minor fractions most probably contain two and three sialic acid residues (exclusively N-acetyleuraminic acid) respectively, thus explaining the different electrophoretic mobilities. The sialic-acid content has been calculated on the basis of a molecular weight of 77500 as determined both by low-speed equilibrium ultracentrifugation and by Archibald's method...

Rabbit antibody light chains: selective breeding narrows variability in framework and complementarity-determining residues

The amino acid sequence of 5 light (L) chain (b4) variable (Vl) regions and the partial sequence of VL (kappa) regions from 12 anti-streptococcal group A-varant polysaccharide (Av-CHO) and 2 anti-streptococcal group C polysaccharide (C-CHO) antibodies was determined. These sequences contain 70 invariant positions as opposed to 50 invariant positions in other rabbit VL regions. Variability within the framework residues lacks randomness, and parent offspring relationship or otherwise close familial relationship is apparent in several instances. Variability in the complementarity-determining regions is reduced by 2.3-5.5-fold in comparison with other rabbit L-chains with several identical first and third hypervariable regions. Residue positions 50-56, known to mark the second hypervariable region in human kappa-chains, are not hypervariable in L-chains from Av-CHO rabbit antibodies. Considering the 67 rabbit L-chain sequences, completely or partially known today, for counting the number of V region germ line genes, it is concluded that the species rabbit has at least 27 VL germ line genes available.

Human and murine phosphorycholine-binding immunoglobulins: conserved subgroup and first hypervariable region of heavy chains

The NH2-terminal 36 residues of the heavy chain and the NH2-terminal 40 residues of the light chain from a human Waldenström's IgM with binding activity for phosphorylcholine (phosphocholine) are compared with the published sequences of five mouse IgA myeloma proteins with the same activity. An extensive structural similarity; i.e., 3 amino acid interchanges within framework residues, and one in the hypervariable region, is noted between the heavy chains of both species. The light chains, however, show a considerable diversity and, in contrast to the heavy chain, no correlation between the primary structure of the first hypervariable region and the binding specificity is apparent. The finding of a very similar heavy chain variable region in two different species that are separated by about 75 million years in evolution favors the concept of stable transmission of variable region genes throughout evolution.

Does a bacterial elongation factor share a common evolutionary ancestor with actin?

Protein synthesis elongation factor Tu from E. coli shares several physical, chemical, and functional properties with actin-like proteins. Limited tryptic degradation indicates that the two polypeptides have a similar molecular architecture. These observations suggest that they could have evolved from a common ancestor, although more information will be necessary to prove or disprove this hypothesis. A partial sequence, comprising 22 aminoacid residues from the aminoterminal end of the large tryptic fragment of elongation factor Tu is presented.