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Biomedical subjects

C Hasemann

Publications and source records attributed to C Hasemann.

5 recordsLinked to original sources
PubMed1989

Structural characterization of antiidiotypic antibodies. Evidence that Ab2s are derived from the germline differently than Ab1s.

We have found that syngeneic Ab2s in the antiarsonate system are serologically and structurally similar to one another. In contrast, the allogeneic Ab2 response is heterogeneous and derives from a large number of unrelated germline gene segments. The Ab2 response of the BALB/c strain to polyclonal A/J Ars A molecules can probably best be compared with a response to a foreign protein and might have been predicted in a strain that completely lacks the H chain V region gene from which the Ab1 derives. Partial variable region sequences of Ab2s from three other systems in addition to previously reported Ab2 structures indicates that this difference in allogeneic vs. syngeneic Ab2s may be a general phenomena. These data support Jerne's hypothesis of complementary V region genes existing in the germline. However, there is good evidence that these antiidiotypic antibodies are not derived directly from the germline, as somatic processes most likely play an important role in their generation. The D segments of Ab2s in the arsonate system as well as in other systems, are novel in structure and cannot easily be explained by previously described germline D segments. D-D fusion may play a role in the generation of the third hypervariable region in these antibodies.

Amino Acid Sequence↗
PubMed1989

Primary structure of the porin protein of Haemophilus influenzae type b determined by nucleotide sequence analysis.

Sequencing techniques for single- and double-stranded DNA were used to determine the nucleotide sequence of the gene encoding P2, the major outer membrane (porin) protein of Haemophilus influenzae type b (Hib). The open reading frame encoding the P2 protein comprised 361 amino acid codons. Comparison of the inferred amino acid sequence with data obtained by amino acid sequencing of the N terminus of the mature or fully processed P2 protein revealed that this protein has a signal peptide composed of 20 amino acids. N-terminal amino acid sequencing of tryptic peptides derived from purified P2 allowed direct identification of 158 of the 341 amino acids in the fully processed P2 protein; there was 100% correlation between these amino acid sequences and that inferred from the nucleotide sequence. The amino acid sequence of Hib P2 protein had 23 to 25% homology with the sequence of the OmpF porin of Escherichia coli and with that of the Neisseria gonorrhoeae porin P.IA. Codon usage in the Hib P2 gene was significantly different from that observed for a gene encoding a porin of E. coli. DNA hybridization studies indicated that there is a single copy of the P2 gene in the Hib chromosome. The availability of the nucleotide and amino acid sequences for the Hib P2 protein will facilitate investigation of the antigenic characteristics and structure-function relationship of this porin.

Amino Acid Sequence↗
PubMed1988

Specific cleavage of diphtheria toxin by human urokinase.

Diphtheria toxin must undergo a specific cleavage reaction and subsequent reduction to express the enzymatic ADP-ribosyltransferase activity that is responsible for its toxicity. In an effort to identify potential cellular enzymes that might be involved in this process we have found that a human urinary plasminogen activator, urokinase, is capable of specifically cleaving diphtheria toxin to yield an enzymatically active A fragment (more homogeneous than that produced by trypsin cleavage) and a B fragment (with an identical amino-terminal sequence to that produced by trypsin cleavage). The results raise the possibility that urokinase or urokinase-like enzymes play a role in diphtheria toxin-mediated intoxication.

Amino Acid Sequence↗