A new family of heparin-binding factors: strong conservation of midkine (MK) sequences between the human and the mouse

A retinoic acid responsive gene, MK, specifies for a heparin binding factor termed midkine (MK), which is the initial member of a new protein family involved in regulation of growth and differentiation. A cDNA clone of human MK was isolated from a fetal kidney cDNA library. Human MK mRNA was expressed in PA1 teratocarcinoma cells as well as in the kidney. Sequence analysis of the cDNA clone and of a part of the genomic clone yielded the predicted protein sequence of human MK. Human and mouse MK sequences are highly conserved: 87% of amino acids are identical and all amino acid changes are conservative except for an insertion. Comparison of MK and HB-GAM/pleiotrophin (another member of the family) from various species revealed sequences conserved in the family and those specific for each protein.     

Expression of mRNA for activin-binding protein (follistatin) during early embryonic development of Xenopus laevis.

Follistatin is a specific activin-binding protein and is supposed to control activin functions. During Xenopus embryonic development, activin is thought to act as a natural mesoderm-inducing factor. We isolated here the Xenopus follistatin cDNA from Xenopus ovary cDNA library and studied the expression of Xenopus follistatin gene during the course of early embryonic development. The Xenopus follistatin has an 84% homology at the level of deduced amino acid sequence with human and porcine follistatin. Its 3.5 kb mRNA is first expressed at the gastrula stage, when the expression of activin mRNA becomes first detectable, and increased thereafter. Another species of 2 kb mRNA become detectable from early neurula and also increased dramatically in tadpole. These results suggest that the follistatin acts also as a regulator of activin in inductive interactions during amphibian embryonic development.     

Structure of a retinoic acid-responsive gene, MK, which is transiently activated during the differentiation of embryonal carcinoma cells and the mid-gestation period of mouse embryogenesis

MK is a gene that is expressed temporarily during the early stages of retinoic acid-induced differentiation of embryonal carcinoma (EC) cells and during the mid-gestation period of mouse embryogenesis. The 5'-regions of MK cDNAs and their mRNAs are heterogeneous; so far three kinds of MK cDNAs (MK1, MK2, and MK3) have been isolated. The MK gene was cloned from a genomic DNA library of a BALB/c mouse, and its structure was elucidated. 5'-Region sequences specific for MK1, MK2, and MK3 were arranged in the order of MK3, MK2, and MK1. Then, there was a sequence common to all MK cDNAs consisting of four exons. The results indicate that different species of MK mRNA are generated by the use of alternative promoters and different modes of splicing.     

Molecular cloning and nucleotide sequences of the complementary DNAs to chicken skeletal muscle myosin two alkali light chain mRNAs.

We report here the molecular cloning and sequence analysis of DNAs complementary to mRNAs for myosin alkali light chain of chicken embryo and adult leg skeletal muscle. pSMA2-1 contained an 818 base-pair insert that includes the entire coding region and 5' and 3' untranslated regions of A2 mRNA. pSMA1-1 contained a 848 base-pair insert that included the 3' untranslated region and almost all of the coding region except for the N-terminal 13 amino acid residues of the A1 light chain. The 741 nucleotide sequences of A1 and A2 mRNAs corresponding to C-terminal 141 amino acid residues and 3' untranslated regions were identical. The 5' terminal nucleotide sequences corresponding to N-terminal 35 amino acid residues of A1 chain were quite different from the sequences corresponding to N-terminal 8 amino acid residues and of the 5' untranslated region of A2 mRNA. These findings are discussed in relation to the structures of the genes for A1 and A2 mRNA.     

Specific photoisomerization of retinal in squid rhodopsin and metarhodopsin

The composition of retinal isomers in the photosteady-state mixtures formed from squid rhodopsin and metarhodopsin was determined by high-pressure liquid chromatography. A large amount of 9-cis-retinal was obtained at liquid N₂ temperature when rhodopsin was irradiated with orange light, but only small quantities of 9-cis-retinal were obtained at 15°C. Scarcely any 9-cis-retinal was produced from metarhodopsin by irradiation at liquid N₂ temperature. A large quantity of 7-cis-retinal was found in the photoproduct of rhodopsin irradiated at solid carbon dioxide temperature, but not at 15°C and liquid N₂ temperature. 7-cis-Retinal was not produced from metarhodopsin at any temperatures. These results indicate that the photoisomerization of retinal is regulated by the structure of the retinal-binding site of this protein. The formation of 9-cis- and 7-cis-retinals is forbidden in the metarhodopsin protein.     

Construction of a physical map of a kanamycin (Km) transposon, Tn5, and a comparison to another km transposon, Tn903

Summary A cleavage map of Tn5, a kanamycin (Km) transposon from plasmid JR67, was constructed from pMKI, a composite plasmid of ColE1 and Tn5, and compared to that of Tn903, a Km transposon from plasmid R6-5. The two transposons showed marked heterogeneity in both the structural gene for Km resistance and the inverted repeat regions as evidenced by their distinctly different restriction maps. This result suggests separate paths of evolution for the two Km transposons.     

Photoreaction of tyrosin-iodinated bacteriorhodopsin at low temperature

To elucidate the role of tyrosine residues in the shift of max and the light-driven proton pump of bacteriorhodopsin~ the photochemical reaction of tyrosine-iodinated bacteriorhodopsin (tyr-mod-bR) was investigated by low-temperature spectrophotometry. After 4–5 of 11 tyrosine residues of bacteriorhodopsin were iodinated, the meta-intermediate of tyr-mod-bR in 75% glycerol solution became so stable that its decay could be observed even at room temperature and i t was stable in the dark for several hours at –65°C.Four batho-intermediates were formed by irradiation with green light (500 nm) at –170°C. Like native bacteriorhodopsin, these batho-intermediates were photoreversible at –170°C. Four corresponding meta-intermediates were also formed by irradiation at –60°C. Using the difference spectra between meta-intermediates and tyr-mod-bR, the absorption spectra of four kinds of tyr-mod-bRs, batho-intermediates, and meta-intermediates were estimated. Each was at shorter wavelengths than that of its corresponding type in native bacteriorhodopsin. The results indicate that two or more tyrosine residues have some role in determining color in native bacteriorhodopsin.     

High-mannose glycopeptides from embryonal carcinoma cells

Endo-beta-N-acetylglucosaminidase H released four major oligosaccharides from high-mannose glycopeptides prepared from embryonal carcinoma cells. The oligosacchaides were indistinguishable from (Man)9GlcNAc, (Man)8GlcNAc, (Man)7GlcNAc, and (Man)6GlcNAc isolated from fibroblasts. This result suggests that the biosynthetic pathway of asparagine-linked oligosaccharides in early embryonic cells is controlled as in adult cells, at least to the initial stage of processing of the nascent oligosaccharide transferred from lipid-linked intermediate.     

Receptors for Dolichos biflorus agglutinin: New cell surface markers on a spontaneous leukemia

$\text{Dolichos biflorus}$ agglutinin (DBA), which is specific for terminal α-N-acetylgalactosamine, bound to a spontaneous leukemia cell of $\text{GRS}\text{A}$ mice, but not to lymphoid cells of the host. The DBA receptors were isolated from the leukemia cell labeled with [³H]-galactose after detergent solubilization and affinity chromatography on DBA-agarose. The major component of the receptors migrated as a glycoprotein of apparent molecular weight 100,000 upon SDS gel electrophoresis. Alkaline treatment degraded the glycoproteins, releasing oligosaccharides of molecular weight around 1,000.