Mapping of mglB, the structural gene of the galactose-binding protein of Escherichia coli

Summary The tetracycline resistance transposon Tn10 was inserted into the E. coli chromosome near mglB550, a structural gene for the galactose-binding protein. P1 transductions established the position of these Tn10 insertions (zee-700, 701, 702::Tn10) close to the genes ptsF, fpk, cdd, mglB550, his, and gatA with 85%–95%, 85%, 36%, 20%–40%, 12%–15%, and 0.5% contransduction frequency. Three factor crosses revealed the relative sequence of the genes as: mglB550, zee-700::Tn10, ptsF, fpk, cdd, his. gatA was found to be 1.3% cotransducible with mglB550. Two Tn10 insertions near gatA were isolated and characterized. One, zef-704::Tn10, was 3% cotransducible with fpk, 8% with mglB550, and 42% with gatA. The other, zef-703::Tn10, was 98% cotransducible with gatA but not with mglB550 or fpk. Neither of these two Tn10 insertions was cotransducible with cdd. Four factor crosses revealed the sequence gatA, zef-704::Tn10, mglB550, fpk.Neither zee-700::Tn10 nor zef-703::Tn10 showed any (0/300) contransduction with either glpT or gyrA. The clockwise order of genes is then: his, cdd, fpk, ptsF, zee-700::Tn10, mglB550, zef-704::Tn10, gatA. With a fix-point for his at 44 min, fpk would be placed at 45 min and mglB550 at 45.5 min. During the course of this work we noticed that the cotransduction frequency between Tn10 insertions and nearby markers tended to increase when new P1 lysates were prepared from freshly reisolated strains. This may indicate loss of nonessential genes adjacent to Tn10 insertions. Using insertion zee-702::Tn10, we isolated deletions extending into an mgl gene other than mglB. Crosses between such a deletion mutant and an mglB550 mutant were done. The analysis of the periplasmic proteins of these as well as other transductants or recombinants involving the mglB550 or the mglB551 gene revealed the existence of strains synthesizing both the wild-type as well as the corresponding mutant protein. Strains containing both proteins exhibit either wild-type or mutant phenotype. These strains appeared unstable. Upon reisolation from purified stock cultures kept in glycerol at-20°C, colonies could be isolated that carried only mutant or wild-type protein.     

Dolichyl phosphate linked sugars as intermediates in the synthesis of yeast mannoproteins: an in vivo study

Freshly prepared protoplasts of Saccharomyces cerevisiae X 2180 incorporate [³H]mannose and [¹⁴C]glucose for about 30 min into glycolipids and mannoproteins. Among the radioactive glycolipids formed dolichyl phosphate mannose, dolichyl phosphate glucose and dolichyl pyrophosphate oligosaccharides have been identified. The oligosaccharides released by weak acid from the dolichyl pyrophosphate were treated with endo-N-acetylglucosaminidase H and separated by gel filtration on Bio-Gel P-4. The largest oligosaccharide obtained corresponded exactly in size to Glc₃Man₉GlcNAc₁ the compound formed also in animal tissues. Other oligosaccharides released from dolichyl pyrophosphate in addition to the glucose containing ones were mainly Man₉GlcNAc₁ and Man₈GlcNAc₁. No mannosyl oligosaccharide corresponding in size to the total inner core region found in native mannoproteins could be detected in a lipid-bound form.The radioactive dolichyl pyrophosphate oligosaccharides were formed transiently; after 40 min only about 40% of the maximal radioactivity was observed in this fraction. In the presence of cycloheximide this decrease did not take place.It is concluded that the dolichol pathway of N-glycosylation of glycoproteins in yeast cells is very similar, if not identical, to the reaction sequence worked out for animal cells.Dedicated to Professor Dr. Otto Kandler on his 60th birthday     

Ferritin as an exogenous yolk protein in snails

Summary A main yolk component in the oocytes of the pulmonate snailPlanorbarius corneus L. has been isolated and identified as the iron storage protein ferritin by its ultrastructure, iron content, immuunological properties and behaviour in disc electrophoresis. As judged from acrylamide electrophoresis data and ultrastructural observations, yolk ferritin is an exogenous protein which is synthesised in the hepatopancreas and taken up by the oocytes by endocytosis.     

Relationship between the chromatoid body and the acrosomal system in early spermatids of Myxine glutinosa L.

Summary A transient close relationship between the chromatoid body and the developing acrosome is demonstrated in early spermatids of Myxine glutinosa.This work was supported by the Norwegian Research Council for Science and Humanities (NAVF, Grant Nr. D 61.44) and the Austrian Fonds zur Förderung der wissenschaftlichen Forschung, Projekt 2183