No abstract

The complete amino acid sequence has been determined for a1B-glycoprotein (a1B), a protein of unknown function present in human plasma. This protein (Mr 63,000) consists of a single polypeptide chain N-linked to four glucosamine oligosaccharides. The polypeptide has five intrachain disulfide bonds and contains 474 amino acid residues. Analysis of the amino acid sequence by several computer programs shows that a1B exhibits internal duplication and consists of five repeating structural domains, each containing about 95 amino acids and one disulfide bond. a1B has a unique amino acid sequence. However, several domains of a1B, especially the third, show statistically significant homology to variable regions of certain immunoglobulin light and heavy chains. ajB also exhibits sequence similarity to other members of the immunoglobulin supergene family such as the receptor for transepithelial transport of IgA and IgM and the secretory component of human IgA. Because of its internal duplication and its sequence homology to immunoglobulin-like proteins, ajB appears to have evolved from an ancestral gene similar to that of the immunoglobulin supergene family.We present the complete amino acid sequence of human aB-glycoprotein (aB) and show that it is homologous in structure to certain domains in immunoglobulins and in the receptor for polymeric immunoglobulins (poly-IgR). a1B was described by Schultze et al. (1) as an "easily precipitable al-glycoprotein" present in human plasma and was later shown to be the same as the aB-glycoprotein observed by Burtin (2) on immunoelectrophoresis of serum. a1B has been reported to have a molecular weight of 68,000 and a carbohydrate content of 13.3% (3). The polypeptide structure was puzzling because a1B appeared to exist in serum in two molecular forms, one having a single polypeptide chain (Mr = 68,000), the other seeming to have two subunits (Mr 50,000 and 20,000). Like most plasma glycoproteins, aIB exhibits electrophoretic heterogeneity near its isoelectric point (pH 4.4-4.6). a1B is present in normal adult serum at an average concentration of 22 mg/dl; however, no change in disease has been observed nor has any biological function been proposed (3). No information on the amino acid sequence of a1B has been reported previously. Thus, aBglycoprotein is one of a series ofhuman plasma glycoproteins of unidentified physiological function that have been highly purified and have been characterized by physicochemical methods but whose primary structure was unknown (3, 4).We are engaged in a program of study of such proteins with the objectives of determining their primary structures, their relationships to other plasma proteins, and their possible functions. Earlier we reported the complete amino acid sequence of p2-glycoprotein I (5), ceruloplasmin (6), hemopexin (7), and leucine-rich a2-glycoprotein (8). A notable structural feature of these four proteins, which is shared by many other plasma proteins (9, 10), is a pattern of internal duplication in amino acid sequence that i...

The principal objective of the space experiment, BRIC-AUX on STS-95, was the integrated analysis of the growth and development of etiolated pea and maize seedlings in space, and the effect of microgravity conditions in space on auxin polar transport in the segments. Microgravity conditions in space strongly affected the growth and development of etiolated pea and maize seedlings. Etiolated pea and maize seedlings were leaned and curved during space flight, respectively. Finally the growth inhibition of these seedlings was also observed. Roots of some pea seedlings grew toward the aerial space of Plant Growth Chamber. Extensibilities of cell walls of the third internode of etiolated pea epicotyls and the top region of etiolated maize coleoptiles which were germinated and grown under microgravity conditions in space were significantly low. Activities of auxin polar transport in the second internode segments of etiolated pea seedlings and coleoptile segments of etiolated maize seedlings were significantly inhibited and extremely promoted, respectively, under microgravity conditions in space. These results strongly suggest that auxin polar transport as well as the growth and development of plants is controlled under gravity on the earth.

No abstract

How microgravitational space environments affect aging is not well understood. We observed that, in Caenorhabditis elegans, spaceflight suppressed the formation of transgenically expressed polyglutamine aggregates, which normally accumulate with increasing age. Moreover, the inactivation of each of seven genes that were down-regulated in space extended lifespan on the ground. These genes encode proteins that are likely related to neuronal or endocrine signaling: acetylcholine receptor, acetylcholine transporter, choline acetyltransferase, rhodopsin-like receptor, glutamate-gated chloride channel, shaker family of potassium channel, and insulin-like peptide. Most of them mediated lifespan control through the key longevity-regulating transcription factors DAF-16 or SKN-1 or through dietary-restriction signaling, singly or in combination. These results suggest that aging in C. elegans is slowed through neuronal and endocrine response to space environmental cues.