NMR studies of a murine-human chimera of leukaemia inhibitory factor (LIF). Comparison with human LIF

Abstract

Leukaemia inhibitory factor (LIF) is a polyfunctional cytokine active on many cell types. We present here 1H NMR studies on the solution properties and stability of MH35, a chimera of murine and human LIF which can be expressed at high levels in Escherichia coli, thus enabling efficient labelling of the protein with the stable isotopes 13C and 15N. MH35 has 85% sequence identity with human LIF and similar activity in biological assays. The 1H chemical shifts of the 12 conserved aromatic residues and the pKa values of the five conserved histidine residues in MH35 and human LIF are very similar. Temperature dependence studies indicate that both proteins are stable, with significant conformatio..