Dear Cheng, Chris and Ruud have provided you with the typical interpretation of such a motif, but you have forgotten to give the CCP4 community the context of this leucine-repeat helix. Is it amphipathic? Does the protein also have transmembrane helices (as suggested by the figure provided) which would provide the membrane anchoring?
Look up structurally similar membrane proteins (not necessarily homologous by sequence), such as proteins which have a monotonic-like membrane interaction, but that also have a transmembrane helix (monoamine oxidase or some mammalian cyt P450s). If your protein is monotopic, look at that class of membrane proteins (squalene cyclase, fatty acid hydrolase, cyclooxygenase, etc.). One structurally undescribed motif is a “reentrant membrane helix.” In other words, look at context before assigning function. Good luck and hope this helps, Michael **************************************************************** R. Michael Garavito, Ph.D. Professor of Biochemistry & Molecular Biology 513 Biochemistry Bldg. Michigan State University East Lansing, MI 48824-1319 Office: (517) 355-9724 Lab: (517) 353-9125 FAX: (517) 353-9334 Email: [email protected] **************************************************************** > On Mar 3, 2018, at 3:51 PM, Cheng Zhang <[email protected]> wrote: > > Hi all, > > We recently got a structure of a transmembrane protein. There is a helix that > is parallel to the membrane. The function of this helix is not known and we > are trying to make some hypothesis. A unique feature is that there are > repeated leucine residues on this helix facing the lipids. I am wondering if > anyone has seen a similar pattern and could suggest possible function, e.g. > membrane anchoring? > > Thanks! > > Best, > > Cheng > > <LeuRHelix.jpg> > > > -- > --------------------- > Cheng Zhang
