Gel filtration of Peking duck eye lens proteins reveals a component eluting just behind δ‐crystallin and comprising approximately 10% of the total soluble protein. The native Mr of this additional component is estimated to be 120000; it appears to be composed of three identical chains of Mr 38000 and pl 7.5. Circular dichroic spectroscopy showed a relatively high α‐helical content. No immunological cross‐reactivity is found with α‐, β‐, γ‐ or δ‐crystallins, and partial amino acid sequence determinations likewise failed to reveal any similarity with other known crystallins. We conclude that this protein represents another and novel family of eye lens proteins, for which we propose the designation ɛ‐crystallin. ɛ‐Crystallin is translated from a 1450‐base mRNA, which has been partially purified. ɛ‐Crystallin is found scattered among avian and reptilian taxa, but not in other vertebrates. Its rate of evolutionary change seems to be as slow as that of α‐ and β‐crystallins.

A model is postulated for the alfalfa mosaic virus (AlMV) coat protein ( M , 24250), consisting of a rigid core and a flexible N-terminal part of approximately 36 amino acid residues. This model is based on a proton nuclear magnetic resonance study of the AlMV coat protein. The NMR spectrum of the coat protein shows several motionally narrowed resonances which strongly decrease in intensity when 25 N-terminal amino acid residues are removed by a mild tryptic treatment. The motionally narrowed resonances, therefore, are assigned to the N-terminal region. Specific assignments in the spectrum for tyrosine-21, threonine-15 and the N-terminal N-acetyl group can be made. The model is supported by photochemically induced dynamic nuclear polarization experiments on the intact protein and the trypsinated protein, which indicate that tyrosine-21 is the only tyrosine which is easily accessible from the solvent. Furthermore, NMR spectra were obtained from a polymerisation product of the coat protein, the so-called 12-S product in which only the sharp resonances of the N-terminal part are observed. Apparently, due to the large particle mass (about 400 kDa), the resonances of the core part of the protein are broadened to such an extent that they are no longer observable. The part of the spectrum which originates from the mobile region of the coat protein can be simulated by calculating a spectrum for a random coil peptide of about 36 N-terminal amino acids. This indicates that the flexible region extends to about 36 amino acid residues from the N terminus and that it probably occurs in a random coil structure. Evidence is presented for a change in structure of the protein in solution when it assembles into the virus particle. This conclusion is based on an observed spectral change of histidine-220.Alfalfa mosaic virus (AlMV) is a plant virus with a tripartite single-stranded RNA genome, encapsidated by one type of coat protein into cylindrical particles of different length with rounded ends. A number of aspects of the structure and assembly of this virus have been described in earlier publications [1,2]. The amino acid sequence of the coat protein is known [3]. Besides its structural function, the coat protein ( M , 24250) plays an essential role in the infection process [4].To obtain a better understanding of this dual nature of the coat protein, knowledge of its structure will be of vital interest. The coat protein is capable of polymerizing into a so-called 3 0 3 particle, a regular spherical ( T = 1) particle, which was shown to consist of 60 copies of the coat protein [5]. Recently, the crystallisation of 30-S particles after mild tryptic digestion has been reported [6] and a X-ray diffraction study is being carried out. However, the tryptic treatment, by which 25 N-terminal amino acid residues are removed, results in a protein that is no longer biologically active [7]. Furthermore, X-ray crystallographic studies do not give information about those parts of the molecule that are in static or dynamic disorder [8] and add...

The structure of the viral RNA in alfalfa mosaic virus (AlMV) was investigated by means of 3'P-nuclear magnetic resonance (NMR). It was found that the 31P-NMR line width of AlMV Top a particles is significantly smaller than that of the larger Bottom particles. At low temperatures, the totational correlation time of the 'P nuclei essentially equals the tumbling rate of the virus particle, indicating that the RNA is contained rigidly inside the virion. At more elevated temperatures, the NMR line width sharpens more than expected on the basis of viscosity changes and the RNA exhibits internal mobility. The occurrence of internal mobility is paralleled by an increased internal mobility of the N-terminal part of the coat protein, as could be observed by 'H-NMR spectroscopy. The influence of EDTA on the 31P-NMR line width appeared to be negligible, which is in agreement with the idea that AlMV does not 'swell' like several other RNA-containing plant viruses.

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