Regulation of haemoglobin synthesis at the polysome level.
B. Colombo, C. Baglioni
Mar 1, 1966
Citations
68
Citations
Quality indicators
Journal
Journal of molecular biology
Full text
Semantic Scholar
Key Takeaway Key Takeaway: The regulation of haemoglobin synthesis in reticulocytes involves -chains being released from polysomes only when -chains are available for combination.
Abstract
The presence of completed peptide chains on reticulocyte polysomes has been studied by incubating the reticulocytes with [14C]arginine or [14C]histidine (the C-terminal amino acid of the α- and β-chain, respectively). The polysomes were isolated and the polysome-bound peptide chains were released and analysed. The C-terminal peptide of the α- and β-chain was isolated after tryptic digestion. 14C activity was demonstrated in the α-chain peptide, whereas the β-chain peptide had very little 14C activity. It has been calculated that one completed α-chain is present on polysomes per five or six growing α-chains. The initial rate of synthesis of haemoglobin peptide chains in rabbit reticulocytes has been studied. After pulse-labelling with [14C]amino acids, more 14C activity was found in β-chains released in the supernatant fraction than in α-chains. The 14C activity of the α-chain equals that of the β-chain after 10 minutes incubation at 20°C. This result is interpreted as meaning that labelled β-chains are initially released associated with unlabelled α-chains, which were present on polysomes before the [14C]amino acid pulse. These results are discussed in connection with the balanced synthesis of haemoglobin peptide chains in reticulocytes. A regulatory mechanism is postulated: α-chains are not released from polysomes unless β-chains are available to combine with them.