Current Insights on the Diverse Structures and Functions in Bacterial Collagen-like Proteins

Abstract

The dearth of knowledge on the diverse structures and functions in bacterial collagen-like proteins is in stark contrast to the deep grasp of structures and functions in mammalian collagen, the ubiquitous triple-helical scleroprotein that plays a central role in tissue architecture, extracellular matrix organization, and signal transduction. To fill and highlight existing gaps due to the general paucity of data on bacterial CLPs, we comprehensively reviewed the latest insight into their functional and structural diversity from multiple perspectives of biology, computational simulations, and materials engineering. The origins and discovery of bacterial CLPs were explored. Their genetic distribution and molecular architecture were analyzed, and their structural and functional diversity in various bacterial genera was examined. The principal roles of computational techniques in understanding bacterial CLPs' structural stability, mechanical properties, and biological functions were also considered. This review serves to drive further interest and development of bacterial CLPs, not only for addressing fundamental biological problems in collagen but also for engineering novel biomaterials. Hence, both biology and materials communities will greatly benefit from intensified research into the diverse structures and functions in bacterial collagen-like proteins.

Prokaryotic Collagen-Like Proteins as Novel Biomaterials

“…Each collagen molecule is made up of three individual α-chains where each α-chain has the structure of a left-handed polyproline Type II-like helix. The three α-chains together form a tightly packed right-handed helix with a 1.5 nm diameter ( Figure 1 ) ( Lodish et al, 2000 ; Berisio et al, 2002 ; Adzhubei, Sternberg, and Makarov 2013 ; Qiu et al, 2021 ). Supercoiling of the individual α-chains in the trimeric structure leads to a rise of 2.9Å per residue and 3.33 residues per turn of the individual α-chains ( Persikov et al, 2000 ).…”

“…Both Scl1 and Scl2 proteins contain a variable number of Gly-X-Y repeats and sequence in their collagen-like region. For example, Scl1 protein from S. pyogenes M1 serotype contains 50 Gly-X-Y repeats whereas Scl2 from serotype M28 contains 79 Gly-X-Y repeats ( Xu et al, 2002 ; Lukomski et al, 2017 ; Qiu et al, 2021 ) ( Figure 2 ).…”

“…S. pneumoniae protein PclA has a collagen-like region interspersed with a non-collagen domain and other small interruptions, and a large C-terminal domain containing an LPXTG motif ( Paterson et al, 2008 ). Within the Bacillus genus, a variety of collagen-like proteins have been reported ( Qiu et al, 2021 ; Leski et al, 2009 ). These are named as Bcl proteins with a corresponding letter at the end e.g.…”

“…Its ubiquity within every animal signifies its importance in the formation and maturation of an organism; thus, it has been the target of many studies from the earlier 1900s through today ( Siegfried 1902 ). These studies have improved the understanding of the structural features of collagens including the Gly-X-Y repeat necessary for its characteristic triple helical structure ( Qiu et al, 2021 ; Chen, Chen, and Horng 2011 ). Understanding the sequence requirement for the triple helix formation led to the discovery that organisms other than animals such as prokaryotes can produce collagen-like proteins as well ( Xu et al, 2002 ; Lukomski et al, 2000 ).…”

“…Understanding the sequence requirement for the triple helix formation led to the discovery that organisms other than animals such as prokaryotes can produce collagen-like proteins as well ( Xu et al, 2002 ; Lukomski et al, 2000 ). Many different species of bacteria have been shown to produce collagen-like proteins, referred in this review article as prokaryotic collagen-like proteins, though the predominantly studied proteins come from the Streptococcus and the Bacillus families of bacteria ( Lukomski et al, 2017 ; Qiu et al, 2021 ). The discovery of these prokaryotic collagen-like proteins has provided a new experimental platform.…”