The complete nucleotide sequence (155 844 bp) of tobacco (Nicotiana tabacum var. Bright Yellow 4) chloroplast DNA has been determined. It contains two copies of an identical 25 339 bp inverted repeat, which are separated by a 86 684 bp and a 18 482 bp single-copy region. The genes for 4 different rRNAs, 30 different tRNAs, 39 different proteins and 11 other predicted protein coding genes have been located. Among them, 15 genes contain introns. Blot hybridization revealed that all rRNA and tRNA genes and 27 protein genes so far analysed are transcribed in the chloroplast and that primary transcripts of the split genes hitherto examined are spliced. Five sequences coding for proteins homologous to components of the respiratory-chain NADH dehydrogenase from human mitochondria have been found. The 30 tRNAs predicted from their genes are sufficient to read all codons if the ;two out of three' and ;U:N wobble' mechanisms operate in the chloroplast. Two sequences which autonomously replicate in yeast have also been mapped. The sequence and expression analyses indicate both prokaryotic and eukaryotic features of the chloroplast genes.

The complete nucleotide sequence of the tobacco chloroplast genome: its gene organization and expression.

Neutron small-angle scattering provides a new tool for investigation of the structure of biological particles. The method is derived from X-ray small-angle scattering. The very large difference between the scattering amplitude of neutrons by hydrogen and deuterium gives the basis of this method, which is explained with reference to the X-ray technique, as both methods have a complementary aspect. Experimental results so far obtained are reviewed, with an emphasis on biological structures composed of two kinds of molecules, such as ribosomes, nucleosomes and viruses.

https://iopscience.iop.org/article/10.1088/0034-4885/39/10/001/pdf

The study of biological structures by neutron scattering from solution

The metabolism of aromatic compounds in higher plants. IV. Purification and properties of the phenylalanine deaminase of Hordeum vulgare.

Recent evidence for evolution of the genetic code.

https://userpages.umbc.edu/~farabaug/lab/papers/annrevgen1996.pdf

Programmed translational frameshifting.

/pdf/crystalline-rhodanese-i-purification-and-physicochemical-lkp0tvvc3f.pdf

Crystalline Rhodanese. I. Purification and Physicochemical Examination.

Structure and function of transfer ribonucleic acid. II. Enzyme-substrate complexes with valyl ribonucleic acid synthetase from yeast.

/pdf/crystalline-rhodanese-ii-the-enzyme-catalyzed-reaction-3aqcitd469.pdf

Crystalline Rhodanese. II. The Enzyme Catalyzed Reaction.

We have investigated the influence of structures in the tRNA anticodon loop and stem on the ability of the anticodon to discriminate among codons. We had previously shown that anticodon UCC, when placed in the structural context of tRNA(Gly1) from Escherichia coli, discriminated efficiently between the glycine codons, as required by the wobble rules. Thus, this anticodon read GGA and GGG but did not read GGU and GGC, whereas in mycoplasma tRNA(Gly), the same anticodon did not discriminate among the glycine codons. We have now determined the reading properties of three constructions based on tRNA(Gly1) containing the anticodon UCC in different structural contexts. In one of these constructs, tRNA(Gly1-ASL), the anticodon loop and stem are the same as in mycoplasma tRNA(Gly). The second construct, tRNA(Gly1-AS), has an anticodon stem identical with the mycoplasma tRNA(Gly), whereas in the last construct, tRNA(Gly1-C32), the only difference from tRNA(Gly1)(UCC) is that the uridine in position 32 of the anticodon loop has been replaced by cytidine. These constructs were tested for ability to read glycine codons in an in vitro protein-synthesizing system that allowed us to monitor separately the reading of each codon. We found that the anticodon UCC, when present in tRNA(Gly1-AS), discriminated among the glycine codons, whereas in the constructs tRNA(Gly1-ASL) and tRNA(Gly1-C32), the same anticodon had lost its ability to discriminate--i.e., it behaved as in mycoplasma tRNA(Gly). These results strongly suggest that nt 32 of the anticodon loop of tRNA(Gly1)(UCC) decisively influences the reading properties of the anticodon UCC.

Ulf Lagerkvist

Papers

Crystalline Rhodanese. I. Purification and Physicochemical Examination.

Structure and function of transfer ribonucleic acid. II. Enzyme-substrate complexes with valyl ribonucleic acid synthetase from yeast.

Crystalline Rhodanese. II. The Enzyme Catalyzed Reaction.

The nucleotide in position 32 of the tRNA anticodon loop determines ability of anticodon UCC to discriminate among glycine codons.

Subunit structure and binding properties of three amino acid transfer ribonucleic acid ligases.