Flagellin that plays both structural and regulatory roles in flagella biosynthesis. Does not constitute a major flagellin in terms of abundance contrary to FlgA1: may regulate the flagella-dependent swimming motility depending on the relative abundance of FlgA1. Not involved in PibD-dependent surface adhesion. Glycosylated by a pentasaccharide similar to the S-layer glycoprotein, probably comprising a hexose, 2 hexuronic acids, a methyl ester of a hexuronic acid and mannose. Straight flagella, mainly at the poles (PubMed:10632878). Cells lacking flgA2 but not flgA1 are hypermotile, display an increased number of flagella per cell, as well as an increased flagellum length (PubMed:23989184). Cells lacking both flgA1 and flgA2 show defects in motility, whitout affecting surface adhesion ability (PubMed:20363933). Belongs to the archaeal flagellin family. Extended N-terminus.