The best diagram i have found so far for surfactant protein D is by Girth Sorensen, and from his diagram I made one in color. I was not successful in finding any molecular structure on the protein database for the N terminal, and have many times sought help finding out about the collagen like domain.  His diagram is pretty regimented, which is not likely to be accurate either because of the arc type shape seen in so many electron micrographs of those arms.  It will try to find out how many repeats there are in the collagen like domain and create a wound structure that more approximates that number.  In the meantime, it is almost laughable how many really bad diagrams of SP-D and SP-A there are in the literature…. the scientific literature, no less, some are really not informative.  But i thought Sorensen’s was close.

One problem with this diagram is its rigidity. Other diagrams have this rigidity of the collagen-like domain as well, but add a quirk in the neck region, bending it at about a 45 degree angle – such a bend apparently located at the beginning of the coiled coil region.  Since I have not found a single diagram with any molecular ribbon or ball and stick diagrams past the neck region, the depiction of a bend at that juncture is a little like fake news.