Exchangeability of silk gland elongation factor 1b and pig liver elongation factor 1beta in polypeptide chain elongation

Expression of elongation factor 1 beta' in Escherichia coli and its interaction with elongation factor 1 alpha from silk gland

Silk gland elongation factor 1 (EF-1) consists of four subunits: alpha, beta, beta', and gamma. EF-1 beta beta' gamma catalyzes the exchange of GDP for GTP on EF-1 alpha and stimulates the binding of EF-1 alpha-dependent aminoacyl-tRNA to ribosomes. The carboxy-terminal regions of the EF-1 beta subunits from various species are highly conserved. We examined the region of EF-1 beta' that binds to EF-1 alpha by in vitro binding assays, and examined the GDP/GTP exchange activity using deletion mutants of a GST-EF1 beta' fusion protein. We thereby suggested a pivotal amino acid region, residues 189-222, of EF-1 beta' for binding to EF-1 alpha.

Expression, purification, and spectroscopic studies of the guanine nucleotide exchange domain of human elongation factor, EF-1beta

Two guanine nucleotide exchange domains, corresponding to the C-terminal region of the human translational elongation factor EF-1beta (which consists of 225 amino acids), were produced by DNA recombinant overexpression techniques in Escherichia coli. We describe here a fast and efficient method for purifying these two protein fragments and for concentrating their solutions rapidly to a level as high as 25 mg/ml. This technique permitted the isolation of 20-30 mg of pure, native protein per liter of bacterial culture. Both fragments were able to form a complex with their natural substrate, elongation factor EF-1alpha, as detected by gel filtration experiments. The domain of 110 residues was slightly more active than the 91-amino-acid domain in guanine nucleotide exchange assays. Folding and stability of the two C-terminal domains were explored by circular dichroism (CD) and NMR spectroscopy. In spite of optimal conditions concerning NaCl concentration, temperature, and pH, during the NMR experiments both proteins showed signs of aggregation after approximately 7 days at 303 degreesK, a time period and temperature required for future heteronuclear NMR experiments. Also, the longer fragment suffered from proteolysis in the N-terminal region, suggestive of flexibility in that part of the structure. The secondary structure content for these two EF-1beta fragments was estimated, using data from both CD and NMR. The results of both methods agree very well and indicate for each fragment the presence of approximately 20% alpha-helix and approximately 50% beta-sheet. Elucidation of the three-dimensional structure of the exchange domain of EF-1beta by NMR spectroscopy appears therefore feasible.

Interactions among four subunits of elongation factor 1 from rice embryo

To establish the subunit construction of elongation factor EF-1, interactions among four non-identical subunits of rice embryo EF-1 (alpha, beta, beta', and gamma) were analyzed with polyacrylamide gel electrophoresis. Complexes beta beta', alpha beta, alpha beta', and beta gamma were formed by mixing the two respective subunits. However, no complex was formed between EF-1 beta' and EF-1 gamma. Complexes containing three subunits like alpha beta beta', alpha beta gamma, and beta beta' gamma, were formed by mixing the three respective subunits. EF-1 was reconstructed when each subunit was added in the following order, beta, beta', gamma, and alpha. The affinity of EF-1 alpha for other subunits was as follows, beta beta' gamma > beta beta' > beta not equal to beta'. Likewise, the affinity of EF-1 gamma for other subunits was: beta beta' gamma > beta >> beta'. Phe-tRNA binding activity of the reconstructed EF-1 was about 90% of that of the native EF-1. From these results, we concluded that rice embryo EF-1 is constructed of equimolar amount of four subunits, alpha, beta, beta' and gamma.

Characterization of the elongation factors from calf brain. 1. Purification, molecular and immunological properties

This work describes a method for the purification of the elongation factors (EF) from calf brain. The elongation factor responsible for the binding of aminoacyl-tRNA to the ribosome is found in this organ as a light form (EF-1 alpha) and as a component of heavy, polydispersed aggregates (EF-1H). EF-1 beta, the factor enhancing the EF-1 alpha GDP/GTP exchange, is part of EF-1H and of smaller aggregates. The fraction of EF-1 alpha and EF-1 beta not associated with EF-1H, and EF-2 have been purified to homogeneity after several chromatographic steps. EF-1H consists of many proteins; among them, EF-1 alpha, EF-1 beta and an EF-1 gamma-like protein represent three of the major components. This conclusively shows that EF-1H from calf brain is not a polydispersed aggregate of only EF-1 alpha. EF-1 beta has also been purified to homogeneity from EF-1H. The property of EF-1 beta to aggregate with other proteins suggests that this factor plays an important role in the organization of EF-1H. The relative molecular mass of the purified factors have been determined as: EF-1 alpha, 50,000; EF-1 beta, 30,000; the EF-1 gamma-like component, 49,000; EF-2, 85,000. Some cross-reactivity with the antibodies against the prokaryotic counterparts has been shown for EF-1 alpha, EF-1 beta and EF-2 by functional and immuno-precipitation methods, suggesting the existence of structural homologies.

A compilation of amino acid analyses of proteins. XVIII. Residues per thousand residues--5

The amino acid analyses of 213 proteins, as residues per 1000 residues, are given. In addition, the carbohydrate content, the content of any noncommon amino acids, the sources of all proteins, and the necessary literature citations are given.

Quantitative data on the Bombyx mori L. silkworm: a review

This paper summarizes a variety of quantitative data on the silkworm Bombyx mori, collected in the literature, to help building models on silk gland differentiation. The properites of the silk gland and their changes especially during the last larval instar have been reviewed (size, DNA, RNA amino acids, enzymes). The components of the silk (fibroin and sericin) are also studied (molecular weight, composition). Thus translation and transcription rates have been estimated. The relevant data on the fat body and the haemolymph are also given, as well as some characteristics of the oocyte/egg system.