PT - JOURNAL ARTICLE AU - C. Nosala AU - K.D. Hagen AU - K. Jones AU - R. Loudermilk AU - K. Nguyen AU - S.C. Dawson TI - <em>Giardia</em>’s ventral disc is hyperstable and composed of over 80 disc-associated proteins AID - 10.1101/361105 DP - 2018 Jan 01 TA - bioRxiv PG - 361105 4099 - http://biorxiv.org/content/early/2018/07/03/361105.short 4100 - http://biorxiv.org/content/early/2018/07/03/361105.full AB - Giardia is a common protistan parasite that causes diarrheal disease worldwide. Motile trophozoites colonize the small intestine, attaching to the villi with the ventral disc, a complex microtubule (MT) organelle. Attachment is required for infection as it allows Giardia to resist peristalsis. Parallel, uniformly spaced MTs spiral to form a domed structure, with one overlap zone between the upper and lower portions, and the ventral groove region extending over the ventral flagella. The MT spiral is coated with novel microribbon-crossbridge protein complexes (MR-CB) that extend up to 400 nm into the cytoplasm. The highly ordered lateral crest lies outside the disc margin at the disc periphery and forms a seal in early staged of parasite attachment. The disc is a hyperstable structure in that drugs that normally affect MT dynamic instability have no effect on ventral disc microtubules and no turnover of any disc-associated protein has been reported. Here we show that much of the ventral disc structure remains intact after detergent extraction in up to 2M potassium chloride. Using a new method of disc biochemical fractionation in high salt with shot-gun proteomic analysis of the disc, we identified and confirmed 55 new disc-associated protein (DAPs), bringing the current total of DAPs to 87. While close to 30 DAPs also localize with flagella, 54 DAPs localize specifically to the disc. Most also localize to specific structural regions of the disc such as the ventral groove or disc margin. Despite our developing understanding of the complexity of ventral disc architecture, we are still in the very preliminary stages of understanding the and composition and contribution of specific structural elements in generating the forces for attachment and stability. Future genetic, biochemical, and functional analyses of DAPs will be central toward understanding not only disc architecture and assembly, but also the overall disc conformational dynamics that promote host attachment.