From reductionism to synthesis: The case of hagfish slime

Biological Materials Processing: Time-Tested Tricks for Sustainable Fiber Fabrication

“… , IFs are a ubiquitous class of cytoskeletal proteins that contribute to the mechanical integrity of living cells but also are harnessed in to make biological materials such as α-keratin, which makes up the outer layer of our skin (stratum cornum) and provides hair and wool with their mechanical integrity. , Like keratin, the IF proteins comprising hagfish slime are rod-like proteins with a central α-helical coiled coil regions and noncoiled N- and C-terminal domains. − The dimeric coiled coils consist of two α helices wrapped around one another in a left-handed supercoil stabilized via hydrophobic interactions due to the conserved presence of nonpolar amino acids on the inner surfaces of the coil. , Similar to spiders, mussels, and velvet worms, the N- and C-terminal domains of IFs are implicated in the higher-order assembly and organization of the fibrillar proteins, although this has not been explicitly demonstrated in the case of hagfish. In hagfish slime, the coiled coils assemble into 12 nm filaments that are further organized into extremely elongated slime threads with a diameter of approximately 2–3 μm but lengths of up to 15 cm, an aspect ratio of up to 75000. , …”

“…Slime formation occurs when the contents of the GTC skeins and GMC mucin vesicles are ejected by the animal and mixed turbulently in a seawater environment (Figure ). Once deployed into the saline and basic conditions of the marine milieu, the skeins of IF-like slime threads unravel to their full length ,, and the mucin vesicles rupture, ,− producing the native slime. Interestingly, the presence of specific ions (especially Ca 2+ and Na + ) results in a more controlled skein unravelling process, suggesting a key role of electrostatic interactions in the material assembly process. , Both components are critical for slime formation; the slime threads by themselves will not form a network, and the mucin material on its own lacks any mechanical consistency .…”

“…In hagfish slime, the coiled coils assemble into 12 nm filaments that are further organized into extremely elongated slime threads with a diameter of approximately 2−3 μm but lengths of up to 15 cm, an aspect ratio of up to 75000. 273,280 Prior to ejection, the slime threads are synthesized and stored within specialized cells (gland thread cells = GTC) in the form of skeins in which the ∼15 cm threads are spooled, resembling an egg-shaped ball of yarn with a major axis of around 150 μm (Figure 16). 37 It has also been hypothesized that organic osmolytes including various methylamines that are present in the slime exudate at a concentration of nearly 0.5 M are also present in the GTCs and may play a role in stabilizing the skein structure.…”