- Incorporation of norleucine at methionine positions in recombinant human macrophage colony stimulating factor (M-CSF, 4-153) expressed in Escherichia coli: structural analysis. Randhawa, Z.I., Witkowska, H.E., Cone, J., Wilkins, J.A., Hughes, P., Yamanishi, K., Yasuda, S., Masui, Y., Arthur, P., Kletke, C. Biochemistry (1994)