CHAPTER 24 – Evolution of Protein Molecules

I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

Principles of Neural Science

Evolution by Gene Duplication

In the genome of a germ-line cell, the genetic information for an immunoglobulin polypeptide chain is contained in multiple gene segments scattered along a chromosome. During the development of bone marrow-derived lymphocytes, these gene segments are assembled by recombination which leads to the formation of a complete gene. In addition, mutations are somatically introduced at a high rate into the amino-terminal region. Both somatic recombination and mutation contribute greatly to an increase in the diversity of antibody synthesized by a single organism.

Somatic generation of antibody diversity

Hybridization of lambda-mRNAs to excess liver DNA yielded results compatible with gene reiteration frequencies of three or less. Purified mRNA from tumors producing structurally different lambda chains were used in competition hybridization experiments. An unlabeled lambda-mRNA competed with another, labelled mRNA to the same extent as homologous unlabelled lambda-mRNA. Mouse DNA was digested with Eco R-I restriction endonuclease and fractionated by gel electrophoresis. A DNA fragment carrying the V lambda-gene(s) was indentified in this digest. This fragment hybridized with lambda-mRNAs coding for two different lambdaV regions equally well. These results indicate that base sequence homology among lambda-mRNAs is so high that any lambda-mRNA should cross-hybridize with all or most of germ line V lambda genes. From amino acid sequence data, it is argued that there are probably more than 25 different lambdaV regions. Hence it is concluded that the number of germ line genes is too small to account for the diversity of lambda chains.

Somatic generation of antibody diversity.

Voltage-dependent anion-selective channel (VDAC) interacts with the dynein light chain Tctex1 and the heat-shock protein PBP74.

Die Primärstruktur der menschlichen freien Sekretkomponente und die Anordnung der Disulfidbrücken

https://www.degruyter.com/view/j/bchm2.1980.361.issue-2/bchm2.1980.361.2.1591/bchm2.1980.361.2.1591.pdf

Präparative Auftrennung des tryptischen Hydrolysats eines Proteins mit Hilfe der Hochdruck-Flüssigkeitschromatographie. Die Primärstruktur einer monoklonalen L-Kette vom K-Typ, Subgruppe I (Bence-Jones-Protein Wes)

We report on the production and characterization of eight monoclonal mouse antibodies against the complete human VDAC "Porin 31HL". The antigen used was purified from a total membrane preparation of the transformed human B-lymphocyte cell line H2LCL. In Western blots all eight mAbs react with a single 31-kDa band in solubilized H2LCL membrane preparations thus demonstrating their specificity for the human VDAC "Porin 31HL". Concerning the epitope specificity we show that all eight mAbs equally react with the N-terminal part of human porin. Moreover, we demonstrate the expression of VDAC in the sarcolemma by indirect immunoenzyme labelling of cryosections of human skeletal muscle applying four of our mAbs. These data support our recent observations on the expression of porin channels in the plasmalemma of different normal and transformed human cell lines. VDAC in the plasmalemma is discussed as the molecular basis of the Blatz and Magleby channel.

Studies on human porin. VI. Production and characterization of eight monoclonal mouse antibodies against the human VDAC "Porin 31HL" and their application for histotopological studies in human skeletal muscle.

Immunoglobulin A which is secreted into external fluids is synthesized in plasma cells as an (IgA)2-J-chain complex. This complex docks on to the polyimmunoglobulin receptor which is located at the basolateral surface of epithelial cells. After docking the (IgA)2-J-receptor complex is internalized and processed. The polyimmunoglobulin receptor loses its C-terminal tail and thus becomes the secretory component. This secretory component is then covalently linked to the (IgA)2-J-chain complex by a disulfide bond, and protects the so formed sIgA from denaturation and proteolysis in external fluids. In order to establish this disulfide bond between IgA and the secretory component, sIgA, purified from human colostrum, was subjected to several enzymatic and chemical fragmentation reactions. One of the resulting polypeptides allowed us to characterize the covalent linkage of the secretory component to IgA in sIgA. IgA was found to be covalently linked to the secretory piece by a single disulfide bond between Cys 311 of one alpha-chain and Cys 467 of the secretory component. Cys 501 of the secretory component and Cys 311 of the other alpha-chain are blocked by cysteines. With this last paper of a series the structure of an entire sIgA molecule has been elucidated.

The Covalent Linkage of Secretory Component to IgA. Structure of sIgA

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