[Protein synthesizing structures and protein synthesis in mouse lymphocytes]

The properties of cytoplasmic mRNP particles from spleen lymphocytes (sedimentation coefficients and buoyant density) and the kinetics of incorporation of impulse amino acid label at definite labelling periods (5, 15, 30, 60 sec) were studied. After 5 or 15 sec labelling periods the labelled amino acid was detected in the polysomes (sedimentation coefficient 130-240S, buoyant density 1.55 g/cm3) and in small-sized particles (sedimentation coefficient 80S and less, buoyant density 1.34, 1.50 and 1.60 g/cm3). After 30 sec of labelling the label is incorporated into the medium-sized particles (sedimentation coefficient 80-120 S, buoyant density 1.47 g/cm3); no increase of the label incorporation into the small-sized particles is observed. After 60 sec the label content in all the three sucrose gradient zones is increased. The observed succession of the amino acid label incorporation first into the small-sized particles and then into the large-sized ones having a different buoyant density and the data from impulse uridyl labelling suggest that in the lymphocytes the translation occurs already in the complexes of informosomes with single ribosomes and continues in the course of their conversion to polysomes. The short-time labelling of the cells with an impulse amino acid label allows to determine the time of the polypeptide chain translation from the time of polysome saturation with the label.