Involved in several steps of L.monocytogenes infection by both intravenous and oral infection (PubMed:16177371). Probably acts as an adhesion; upon ectopic expression in L.innocula bacteria adhere better to human cell lines (PubMed:18227172). Despite being transcribed during bacterial growth in culture the protein is only detected in infected mice. Nearly full-length mature protein and an internal LRR-containing fragment interact in vitro with human intestinal mucin-2 (MUC2) but not with mucin-1. LRR fragment binding is slightly better at pH 5.5, (the pH of the intestine) than at pH 7.4. No protein is expressed when grown in liquid culture; protein is detected 72 hours post-inoculation in intravenously infected mice (PubMed:18227172). Upon expression under control of a heterologous promoter during exponential growth is detected on the cell surface as a series of dots in a helical pattern, it is excluded from the septum; at very high expression levels it accumulates at cell poles (PubMed:21725001). The helical pattern of InlA does not overlap with that of InlH, InlJ or Hbp2 (SvpA) (PubMed:21725001). In stationary phase remains outside of the cell pole and septum (PubMed:21725001). Expressed in late exponential phase. The LRR domain (34-508) binds more efficiently in vitro to human intestinal mucin-2 (MUC2) than does a nearly whole protein (26-792) suggesting the MucBP domains do not function in mucin-binding in Listeria. No visible effect on colonization of host tissue culture cells; decreased organ colonization in mice. Belongs to the internalin family.