Dave Rintoul drintoul at
Mon Apr 3 11:30:28 EST 1995


I am in the process of revising the companion volume for the next
edition of a major cell biology text, due out in the spring of 1995.
These companion volumes consist of questions (and answers) to assist
in learning the mass of material in the text proper.  These questions
start out easy (essentially vocabulary buiding) and progress through
conceptual stuff to the hardest questions, those dealing with analysis
of real experimental data gleaned from the literature.  

I have a question which is pretty basic, regarding the Drosophila
proteins notch and delta.  My understanding of these is that they are
both transmembrane proteins with EGF-like repeats on the extracellular
domain.  They apparently bind to each other; serrate is another
transmembrane protein which seems to bind to notch.  Neither delta nor
notch has any significant homology to other known signaling proteins,
yet one (delta) is thought to be the ligand and the other (notch) is
thought to be a receptor which initiates secondary signalling pathways
in that cell.  My question is:

What is the evidence/logic that supports the identification of one
of these transmembrane proteins as a receptor and the other as
the ligand?  
I have foound and read a couple of reviews on this topic which seem to
gloss over this evidence.  I assume that genetic techniques, perhaps
with naturally occurring mutants or with engineered deletions, etc.
form the basis for this conclusion.  But I would like to use this
example as a model for dissection of other similar systems with
transmembrane ligands and receptors, so I would like a bit of the
history, details etc for this system.  I will acknowledge your
contributions in the preface of the text if I am able to generate a
pedagogically acceptable question/answer.  Thanks in advance.

Dave Rintoul

Dave Rintoul                 Internet: drintoul at
Biology Division - KSU     Latitude 39.18, Longitude -96.34
Manhattan KS 66506-4901                Compuserve: 71634,32
(913)-532-6663 or 5832                  FAX: (913)-532-6653

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