Blood, 1 July 2002, Vol. 100, No. 1, pp. 299-305
TRANSFUSION MEDICINE
Intersubunit circular permutation of human hemoglobin
Kevin E. Sanders,
John Lo, and
Stephen G. Sligar
From the Beckman Institute for Advanced Science and
Technology and the Department of Biochemistry, University of Illinois,
Urbana, IL.
For many years, human hemoglobin (Hb) isolated from erythrocytes
has been investigated as a potential oxygen delivery therapeutic. Advantages with respect to the need for blood typing were balanced with
various undesirable properties of cell-free Hb, including cost, overall
oxygen affinity, alterations in cooperativity, and ready dissociation
into toxic dimeric species. The use of total gene synthesis has
resulted in very high levels of functional human Hb expression in
Escherichia coli, but there remains a desire for effecting
the crosslinking of the hemoglobin tetramer and providing for ready
means for increasing the globular molecular weight. In this
communication, we report a novel method for linking alpha chains. By
circularly permuting one alpha sequence, the second alpha chain in the
Hb tetramer can be linked with glycine residues to form 2 bridges
across the central cavity. The second alpha chain thus presents its
amino and carboxyl termini on a solvent exposed surface, providing for
additional polymerization of oxygen-carrying subunits or attachment of
any other peptide-based therapeutic.
