SP-A exists (according to some published papers) in open and closed configuration…bending i guess only at the N termini juncture, and then again perhaps bending at the CRD and the neck. SP-D in fuzzyball multimers seems to be flexible at the N termini junctures as well, but I have no seen much text about the side to side N terminus connections in SP-D, which in my opinion likely exist similar to SP-A and some other “tulip type configuration” c-type lectin multimers.

Looking only at the “arms” where the collagen-like domains are doesn’t offer much suggestion that there are kinks in SP-D, but does suggest kinks in SP-A (also published data by others).

Here is a nice image (i added the circle over systems aligned with SP-D structure are) which is from a phylo tree from an article by Drickamer and Taylor which shows the collagen-like domain as a more or less straight portion of the 4 part trimer as an example, but without any reference to bumps or bends or lumps and also without any diagramatic representation of the coiled coil neck. Nonetheless it gives a view of the repeated elements in those 6 c-type lectins – which they assign to Group 9 – and i dont know what that signifies yet).