proto- + filament
protofilament (plural protofilaments)
- A filament of polymerized tubulin in a cell, which becomes part of a microtubule
2008 January 22, Mitsusada Iwasa Toshiro Oda & Akihiro Narita da, “The nature of the globular- to fibrous-actin transition”, in Nature, volume 457, number 7228, DOI:10.1038/nature07685:
- The MreB crystal contained a straight, single-stranded protofilament […] .