There does seem to be a dearth of information on this name. The only references on the web are to Americans, no Germans. The site I find useful for American versions of European names is
www.ancestry.com but but they have no entry for Meklune.
For some reason I keep thinking it has a Baltic appearance, Lithuanian or Latvian or even old Prussian. The nearest I can find is Mikalunas (Lithuanian), denoting descent from someone called Michael.
I don't think the Mac- origin can be dimissed out of hand. The Baltic seaport of Elbing in Prussia - now Elblag in Poland - was founded and populated by Scots merchants and traders. I believe some Scottish surnames survive in altered form. Certainly the Scots name MacLeod survived in Poland as Machlejd.