Email: jhn@biochem.umass.edu

Ph.D.: Michigan State University
Postdoctoral Training: University of Minnesota

Biochemical Aspects of insect Embryogenesis

My research interests are focused on a problem that is central to insect development. How does the embryo regulate utilization of its stored nutritive sources for growth? The most important of these is the yolk protein vitellin. Following endocytosis by th e oocyte, vitellin is stored in yolk granules. Subsequent to fertilization, the vitellin polypeptides are processed proteolytically and finally degraded in a controlled manner, consistent with the needs of the embryo. To gain insight into this problem, we are investigating two events correlated temporally with vitellin degradation; the developmentally regulated acidification of the granules by proton translocation, and a vitellin-processing proteinase, which is activated by the acidification. We are also assessing the possible role of unusual embryo cells called vitellophages and of endosymbiont bacteria which reside in the embryo in these events.

Representative publications:

Giorgi, F. Bradley J. and Nordin, J.H. Differential Polypeptide Processing in Insect Embryos (1999) Micron (in the press).

Liu, X. and Nordin, J.H. Localization of the Proenzyme Form of the Vitellin Processing Protease of Blattella germanica by Affinity Purified Antibodies (1998) Arch Insect Biochem. Physiol. 38, 109-118.

Giorgi, F. , Yin, L., Cecchettini, A. and Nordin, J.H. (1997) The Vitellin Processing Protease of Blattella germanica is Derived From a Proprotease of Maternal Origin. Tissue and Cell 28, 293-303.

Liu, X., Mc Carron, R. L. and Nordin, J.H. (1996) A Cysteine Protease Which Processes Insect Vitelli: Purification and Partial Characterization of the Enzyme and the Proenzyme J. Biol. Chem. 271, 33344-33351.