Clemens Kaiser

The location of a second in vivo phosphorylation site in the Aα-chain of human fibrinogen

Abstract By quantitative phosphorus determination on the single chains of human fibrinogen it is demonstrated that the covalently bound phosphorus of adult and fetal fibrinogen is exclusively located in the Aα-chain. The Aα-chain of fetal fibrinogen contains about twice as much phosphorus as the adult Aα-chain in the well known position of Ser 3 of fibrino-peptide A as well as in a hitherto unknown second position on the Aα-chain. By consecutive cleavage of the Aα-chains of fetal and adult fibrinogen with cyanogen bromide, trypsin, and chymotrypsin, separation of the resulting peptide mixtures and analysis for phosphorylated amino acids, this second phosphorylation site could be traced to Ser 345 of the Aα-chain. There is only one sequence homology between the two now known in vivo phosphorylation sites of human fibrinogen, namely that the second amino acid to the carboxyl side of the phosphorylated Ser is Glu. The sequence specificity of the up to now unidentified protein kinase phosphorylating fibrinogen allows it to be classified as a member of the group of type-2 casein kinases or casein kinases TS.

N-terminal amino acid sequences of precursor and mature forms of α-1-antitrypsin

α‐1‐Antitrypsin is found in hepatocytes as a high‐mannose glycoprotein (M r 49000), extracellularly as a complex‐type glycoprotein (M r 54000). Deglycosylation of both forms with peptide: N‐glycosidase led to proteins of identical app. M r (41000). The sequence of 26 N‐terminal amino acids of rat α1‐antitrypsin was determined. A high content of polar amino acids was found. The partially characterized presequence of in vitro synthesized α1‐antitrypsin showed a cluster of hydrophobic amino acids. A pre‐peptide of 24 amino acids is proposed. There is no evidence for the existence of a propeptide.

cis-Oxa,aza-σ-homobenzenes : Syntheses,[2+2+2]-cycloreversion reactions

Abstract cis -Dioxa,aza-tris-(8) and cis -oxa, aza-bis-σ-homobenzenes (21) have been synthesised. With activation barriers, which clearly support the concerted mechanism, they undergo [2+2+2]-cycloreversion yielding 7H-1,4,7-dioxazonines (9) and 4H-1,4-oxazocines (22), resp.

Characterisation of calmodulin from Drosophila heads.

Calmodulin from Drosophila heads has been purified to apparent electrophoretic homogeneity. It has the same characteristics as bovine brain calmodulin with respect to the migration upon polyacrylamide gel electrophoresis and maximal activation of a calmodulin-deficient cAMP phosphodiesterase. The amino acid composition resembles bovine brain calmodulin with the exception that trimethyllysine is absent and that it contains only one tyrosine. The tryptic peptide map of Drosophila calmodulin suggests some differences in the amino acid sequence as compared to bovine brain calmodulin. These proposed differences in the primary structure may explain why Drosophila calmodulin is less potent than bovine brain calmodulin in the activation of a cAMP phosphodiesterase from bovine brain.