Assembly of recently translated full-length and C-terminal truncated human gamma-globin chains with a pool of alpha-globin chains to form Hb F in a cell-free system.
Assembly of alpha-globin with translated, full-length and C-terminal truncated human gamma-globin to form Hb F was assessed in a cell-free transcription/translation system. Polysome profiles showed two amino acid C-terminal-truncated gamma-chains retained on polysomes can assemble with unlabeled holo alpha-chains only after puromycin-induced chain release. Two amino acid C-terminal truncated gamma-chains encoded from vectors containing a stop codon at the translation termination site were released from polysomes and assembled with alpha-chains in the absence of puromycin addition, while removal of 11 or more amino acids from the gamma-chain carboxy-terminus inhibited assembly with alpha-chains. These results suggest that amino acids in the HC- and H-helix gamma-chain regions including amino acids 135-144 at the C-terminus in the translated gamma-chains play a key role in assembly with alpha-chains, and that assembly occurs soon after exit of translated gamma-chains from the ribosome tunnel and release from polysomes thereby preventing stable gamma(2) homo-dimer formation.
Adachi
Kazuhiko
K
The Children's Hospital of Philadelphia, Division of Hematology, University of Pennsylvania School of Medicine, 34th Street & Civic Center Boulevard, Philadelphia, PA 19104, USA. adachi@email.chop.edu
Zhao
Yi
Y
Lakka
Vinaysagar
V
Weiss
Mitchell J
MJ
Surrey
Saul
S
D001798:Blood Proteins / Q000502:physiology; D002474:Cell-Free System; D005319:Fetal Hemoglobin / Q000096:biosynthesis*; D005914:Globins / Q000378:metabolism*; D006801:Humans; D018832:Molecular Chaperones / Q000502:physiology; D011132:Polyribosomes / Q000378:metabolism; D014908:Triticum / Q000378:metabolism
C468768:AHSP protein, human; D001798:Blood Proteins; D018832:Molecular Chaperones; D005914:Globins; D005319:Fetal Hemoglobin