Turns in beta-alpha-beta loops (protein motifs)

In the context of protein secondary structure, do the loops between strand and helix in a [beta-alpha-beta motif](http://www.cryst.bbk.ac.uk/PPS95/course/6_super_sec/super5.html) form into the conformation known as a [beta turn](https://en.wikipedia.org/wiki/Beta_turn)?




So a beta-alpha-beta structure will have two loops that could be turns - between the first beta strand and the alpha helix, and the helix and the second strand. They *might* be beta turns, but they might not.


Although there are different definitions of beta-turns, one common one is the presence of a hydrogen bond between the carbonyl of residue (i) and the amino of residue (i+3). I'm not actually sure how frequent this is, but you can see this from a search on [PDBeMotif](http://www.ebi.ac.uk/pdbe-site/pdbemotif/). There is also [Motivated Proteins](http://motif.gla.ac.uk/motif/index.html), which gives nice 2D (and 3D) images of motifs.


However, you could get other conformations of these loops that are not beta-turns, especially if they are quite long.


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