Structural comparison of ColH and ColG collagen-binding domains from Clostridium histolyticum

Overview of Bacterial Protein Toxins from Pathogenic Bacteria: Mode of Action and Insights into Evolution

Bacterial protein toxins are secreted by certain bacteria and are responsible for mild to severe diseases in humans and animals. They are among the most potent molecules known, which are active at very low concentrations. Bacterial protein toxins exhibit a wide diversity based on size, structure, and mode of action. Upon recognition of a cell surface receptor (protein, glycoprotein, and glycolipid), they are active either at the cell surface (signal transduction, membrane damage by pore formation, or hydrolysis of membrane compound(s)) or intracellularly. Various bacterial protein toxins have the ability to enter cells, most often using an endocytosis mechanism, and to deliver the effector domain into the cytosol, where it interacts with an intracellular target(s). According to the nature of the intracellular target(s) and type of modification, various cellular effects are induced (cell death, homeostasis modification, cytoskeleton alteration, blockade of exocytosis, etc.). The various modes of action of bacterial protein toxins are illustrated with representative examples. Insights in toxin evolution are discussed.

Discovery and Characterization of Synthesized and FDA-Approved Inhibitors of Clostridial and Bacillary Collagenases

In view of the worldwide antimicrobial resistance (AMR) threat, new bacterial targets and anti-infective agents are needed. Since important roles in bacterial pathogenesis have been demonstrated for the collagenase H and G (ColH and ColG) from Clostridium histolyticum, collagenase Q1 and A (ColQ1 and ColA) from Bacillus cereus represent attractive antivirulence targets. Furthermore, repurposing FDA-approved drugs may assist to tackle the AMR crisis and was addressed in this work. Here, we report on the discovery of two potent and chemically stable bacterial collagenase inhibitors: synthesized and FDA-approved diphosphonates and hydroxamates. Both classes showed high in vitro activity against the clostridial and bacillary collagenases. The potent diphosphonates reduced B. cereus-mediated detachment and death of cells and Galleria mellonella larvae. The hydroxamates were also tested in a similar manner; they did not have an effect in infection models. This might be due to their fast binding kinetics to bacterial collagenases.

A gold revision of the Golgi Dynamics (GOLD) domain structure and associated cell functionalities

The classical secretory pathway is the key membrane-based delivery system in eukaryotic cells. Several families of proteins involved in the secretory pathway, with functionalities going from cargo sorting receptors to the maintenance and dynamics of secretory organelles, share soluble globular domains predicted to mediate protein-protein interactions. One of them is "Golgi Dynamics" (GOLD) domain, named after its strong association with the Golgi apparatus. There are many GOLD-containing protein families, such as the Transmembrane emp24 domain-containing proteins (TMED/p24 family), animal SEC14-like proteins, Human Golgi resident protein ACBD3, a splice variant of TICAM2 called TRAM with GOLD domain and FYCO1. Here, we critically review the state-of-the-art knowledge of the structures and functions of the main representatives of GOLD-containing proteins in vertebrates. We provide the first unified description of the GOLD domain structure across different families since the first high-resolution structure was determined. With a brand-new update on the definition of the GOLD domain, we also discuss how its tertiary structure fits the β-sandwich-like fold map and give exciting new directions for forthcoming studies.

Biochemical characterisation of a collagenase from Bacillus cereus strain Q1

Collagen is the most abundant protein in higher animals and as such it is a valuable source of amino acids and carbon for saprophytic bacteria. Due to its unique amino acid composition and triple-helical tertiary structure it can however only be cleaved by specialized proteases like the collagenases secreted by some bacteria. Among the best described bacterial collagenases are ColG and ColH from Clostridium histolyticum. Many Bacillus species contain homologues of clostridial collagenases, which play a role in some infections caused by B. cereus. Detailed biochemical and enzymatic characterizations of bacillial collagenases are however lacking at this time. In an effort to close this gap in knowledge we expressed ColQ1 from B. cereus strain Q1 recombinantly, investigated its metal dependency and performed peptide, gelatin and collagen degradation assays. Our results show that ColQ1 is a true collagenase, cleaving natively folded collagen six times more efficiently than ColG while at the same time being a similarly effective peptidase as ColH. In both ColQ1 and ColG the rate-limiting step in collagenolysis is the unwinding of the triple-helix. The data suggest an orchestrated multi-domain mechanism for efficient helicase activity.

Mechanistic Insight into the Binding and Swelling Functions of Prepeptidase C-Terminal (PPC) Domains from Various Bacterial Proteases

The bacterial prepeptidase C-terminal (PPC) domain can be found in the C termini of a wide variety of proteases that are secreted by marine bacteria. However, the functions of these PPC domains remain unknown due to a lack of systematic research. Here, the binding and swelling abilities of eight PPC domains from six different proteases were compared systematically via scanning electron microscopy (SEM), enzyme assays, and fluorescence spectroscopy. These PPC domains all possess the ability to bind and swell insoluble collagen. PPC domains can expose collagen monomers but cannot disrupt the pyridinoline cross-links or unwind the collagen triple helix. This ability can play a synergistic role alongside collagenase in collagen hydrolysis. Site-directed mutagenesis of the PPC domain from Vibrio anguillarum showed that the conserved polar and aromatic residues Y6, D26, D28, Y30, W42, E53, C55, and Y65 and the hydrophobic residues V10, V18, and I57 played key roles in substrate binding. Molecular dynamic simulations were conducted to investigate the interactions between PPC domains and collagen. Most PPC domains have a similar mechanism for binding collagen, and the hydrophobic binding pocket of PPC domains may play an important role in collagen binding. This study sheds light on the substrate binding mechanisms of PPC domains and reveals a new function for the PPC domains of bacterial proteases in substrate degradation.IMPORTANCE Prepeptidase C-terminal (PPC) domains commonly exist in the C termini of marine bacterial proteases. Reports examining PPC have been limited, and its functions remain unclear. In this study, eight PPCs from six different bacteria were examined. Most of the PPCs possessed the ability to bind collagen, feathers, and chitin, and all PPCs could significantly swell insoluble collagen. PPCs can expose collagen monomers but cannot disrupt pyridinoline cross-links or unwind the collagen triple helix. This swelling ability may also play synergistic roles in collagen hydrolysis. Comparative structural analyses and the examination of PPC mutants revealed that the hydrophobic binding pockets of PPCs may play important roles in collagen binding. This study provides new insights into the functions and ecological significance of PPCs, and the molecular mechanism of the collagen binding of PPCs was clarified, which is beneficial for the protein engineering of highly active PPCs and collagenase in the pharmaceutical industry and of artificial biological materials.

Acceleration of bone regeneration of horizontal bone defect in rats using collagen-binding basic fibroblast growth factor combined with collagen scaffolds

Background

Basic fibroblast growth factor (bFGF) has been applied for periodontal regeneration. However, the application depends on bone defect morphology because bFGF diffuses rapidly from defect sites. In a previous study, collagen‐binding bFGF (CB‐bFGF) has been shown to enhance bone formation by collagen‐anchoring in the orthopedic field. The aim of this study is to demonstrate the efficacy of CB‐bFGF with collagen scaffolds in bone regeneration of horizontal bone defect.

Methods

Cell proliferation activity and collagen binding activity of CB‐bFGF was confirmed by WST‐8 assay and collagen binding assay, respectively. The retention of CB‐bFGF in the collagen sheet (CS) was measured by fluorescence imaging. The rat horizontal alveolar bone defect model was employed to investigate the efficacy of CB‐bFGF with collagen powder (CP). After 4 and 8 weeks, the regenerative efficacy was evaluated by microcomputed tomography, histological, and immunohistochemical analyses.

Results

CB‐bFGF had a comparable proliferation activity to bFGF and a collagen binding activity. CB‐bFGF was retained in CS longer than bFGF. At 8 weeks postoperation, bone volume, bone mineral content, and new bone area in CB‐bFGF/CP group were significantly increased compared with those in other groups. Furthermore, epithelial downgrowth was significantly suppressed in CB‐bFGF/CP group. At 4 weeks, the numbers of osteocalcin, proliferating cell nuclear antigen, and osteopontin‐positive cells at the regeneration site in CB‐bFGF/CP group were greater than those in other groups.

Conclusions

CB‐bFGF/CP effectively promoted bone regeneration of horizontal bone defect possibly by sustained release of bFGF. The potential of CB‐bFGF composite material for improved periodontal regeneration in vertical axis was shown.

The Characteristics of Intrinsic Fluorescence of Type I Collagen Influenced by Collagenase I

The triple helix structure of collagen can be degraded by collagenase. In this study, we explored how the intrinsic fluorescence of type I collagen was influenced by collagenase I. We found that tyrosine was the main factor that could successfully excite the collagen fluorescence. Initially, self-assembly behavior of collagen resulted in a large amount of tyrosine wrapped with collagen, which decreased the fluorescence intensity of type I collagen. After collagenase cleavage, some wrapped-tyrosine could be exposed and thereby the intrinsic fluorescence intensity of collagen increased. By observation and analysis, the influence of collagenase to intrinsic fluorescence of collagen was investigated and elaborated. Furthermore, collagenase cleavage to the special triple helix structure of collagen would result in a slight improvement of collagen thermostability, which was explained by the increasing amount of terminal peptides. These results are helpful and effective for reaction mechanism research related to collagen, which can be observed by fluorescent technology. Meantime, the reaction behaviors of both collagenase and collagenolytic proteases can also be analyzed by fluorescent technology. In conclusion, this research provides a foundation for the further investigation of collagen reactions in different areas, such as medicine, nutrition, food and agriculture.

The C-terminal segment of collagenase in Grimontia hollisae binds collagen to enhance collagenolysis

The collagenase secreted by Grimontia hollisae strain 1706B is a 74 kDa protein that consists of two parts: the catalytic module and a C‐terminal segment that includes the bacterial pre‐peptidase C‐terminal domain. Here, we produced a recombinant C‐terminal segment protein and examined its ability to bind collagen and other characteristics as compared with collagen‐binding domains (CBDs) derived from Hathewaya histolytica (Clostridium histolyticum) collagenases; these CBDs are the only ones thus far identified in bacterial collagenases. We found that the C‐terminal segment binds to collagen only when the collagen is in its triple‐helical conformation. Moreover, the C‐terminal segment and the CBDs from H. histolytica have comparable characteristics, including binding affinity to type I collagen, substrate spectrum, and binding conditions with respect to salt concentration and pH. However, the C‐terminal segment has a completely different primary structure from those of the CBDs from H. histolytica. As regards secondary structure, in silico prediction indicates that the C‐terminal segment may be homologous to those in CBDs from H. histolytica. Furthermore, we performed collagenase assays using fluorescein isothiocyanate‐labeled type I collagen to show that the C‐terminal segment positively contributes to the collagenolytic activity of the 74 kDa collagenase from G. hollisae.

Ca2+ -induced orientation of tandem collagen binding domains from clostridial collagenase ColG permits two opposing functions of collagen fibril formation and retardation

To penetrate host tissues, histotoxic clostridia secrete virulence factors including enzymes to hydrolyze extracellular matrix. Clostridium histolyticum, recently renamed as Hathewaya histolytica, produces two classes of collagenase (ColG and ColH). The high-speed AFM study showed that ColG collagenase moves unidirectionally to plane collagen fibril and rebundles fibril when stalled . The structural explanation of the roles for the tandem collagen-binding segment (CBDs) is illuminated by its calcium-bound crystal structure at 1.9 Å resolution (R_work = 15.0%; R_free = 19.6%). Activation may involve calcium-dependent domain rearrangement supported by both small-angle X-ray scattering and size exclusion chromatography. At pCa ≥ 5 (pCa = -log[Ca²⁺ ]), the tandem CBD adopts an extended conformation that may facilitate secretion from the bacterium. At pCa ≤ 4, the compact structure seen in the crystal structure is adopted. This arrangement positions the two binding surfaces ~ 55 Å apart, and possibly ushers ColG along tropocollagen molecules that allow for unidirectional movement. A sequential binding mode where tighter binding CBD2 binds first could aid in processivity as well. Switch from processive collagenolysis to fibril rearrangement could be concentration dependent. Collagen fibril formation is retarded at 1 : 1 molar ratio of tandem CBD to collagen. Tandem CBD may help isolate a tropocollagen molecule from a fibril at this ratio. At 0.1 : 1 to 0.5 : 1 molar ratios fibril self-assembly was accelerated. Gain of function as a result of gene duplication of CBD for the M9B enzymes is speculated. The binding and activation modes described here will aid in drug delivery design.

ACCESSION CODES

The full atomic coordinates of the tandem CBD and its corresponding structure factor amplitudes have been deposited in the Protein Data Bank (PDB accession code 5IKU). Small-angle X-ray scattering data and corresponding ab initio models have been submitted to the Small Angle Scattering Biological Data Bank (SASBDB). Accession codes CL2, collagenase module 2, CN2, CP2 are assigned to envelopes for tandem CBD at -log[Ca²⁺ ] (pCa) 3, 4, 5, and 6, respectively. Accession code DC64 was assigned to the complex of polycystic kidney disease-CBD1-CBD2 with mini-collagen.

Basic Fibroblast Growth Factor Fused with Tandem Collagen-Binding Domains from Clostridium histolyticum Collagenase ColG Increases Bone Formation

Basic fibroblast growth factor 2 (bFGF) accelerates bone formation during fracture healing. Because the efficacy of bFGF decreases rapidly following its diffusion from fracture sites, however, repeated dosing is required to ensure a sustained therapeutic effect. We previously developed a fusion protein comprising bFGF, a polycystic kidney disease domain (PKD; s2b), and collagen-binding domain (CBD; s3) sourced from the Clostridium histolyticum class II collagenase, ColH, and reported that the combination of this fusion protein with a collagen-like peptide, poly(Pro-Hyp-Gly)₁₀, induced mesenchymal cell proliferation and callus formation at fracture sites. In addition, C. histolyticum produces class I collagenase (ColG) with tandem CBDs (s3a and s3b) at the C-terminus. We therefore hypothesized that a bFGF fusion protein containing ColG-derived tandem CBDs (s3a and s3b) would show enhanced collagen-binding activity, leading to improved bone formation. Here, we examined the binding affinity of four collagen anchors derived from the two clostridial collagenases to H-Gly-Pro-Arg-Gly-(Pro-Hyp-Gly)₁₂-NH₂, a collagenous peptide, by surface plasmon resonance and found that tandem CBDs (s3a-s3b) have the highest affinity for the collagenous peptide. We also constructed four fusion proteins consisting of bFGF and s3 (bFGF-s3), s2b-s3b (bFGF-s2b-s3), s3b (bFGF-s3b), and s3a-s3b (bFGF-s3a-s3b) and compared their biological activities to those of a previous fusion construct (bFGF-s2b-s3) using a cell proliferation assay in vitro and a mouse femoral fracture model in vivo. Among these CB-bFGFs, bFGF-s3a-s3b showed the highest capacity to induce mesenchymal cell proliferation and callus formation in the mice fracture model. The poly(Pro-Hyp-Gly)₁₀/bFGF-s3a-s3b construct may therefore have the potential to promote bone formation in clinical settings.

Alternate carbohydrate and nontraditional inducer leads to increased productivity of a collagen binding domain fusion protein via fed-batch fermentation

The production of collagen binding domain fusion proteins is of significant importance because of their potential as therapeutic biomaterials. It was previously reported that the expression of collagen-binding domain fusion proteins in Escherichia coli was higher when expressed using lactose as an inducer and chemically defined growth media on a shake flask scale. In an effort to further investigate factors that affect expression levels on a fed-batch scale, alternative induction techniques were tested in conjunction with fed-batch fermentation. In this paper, we discuss ten fed-batch fermentation experiments utilizing either glucose or glycerol feed and using lactose or isopropyl-β-d-thiogalactopyranoside (IPTG) as an induction source. It was found that glycerol-fed fermentations induced with lactose allowed for greater expression of target protein, though lesser cell densities were achieved.

Collagen interactions: Drug design and delivery

Collagen is a major component in a wide range of drug delivery systems and biomaterial applications. Its basic physical and structural properties, together with its low immunogenicity and natural turnover, are keys to its biocompatibility and effectiveness. In addition to its material properties, the collagen triple-helix interacts with a large number of molecules that trigger biological events. Collagen interactions with cell surface receptors regulate many cellular processes, while interactions with other ECM components are critical for matrix structure and remodeling. Collagen also interacts with enzymes involved in its biosynthesis and degradation, including matrix metalloproteinases. Over the past decade, much information has been gained about the nature and specificity of collagen interactions with its partners. These studies have defined collagen sequences responsible for binding and the high-resolution structures of triple-helical peptides bound to its natural binding partners. Strategies to target collagen interactions are already being developed, including the use of monoclonal antibodies to interfere with collagen fibril formation and the use of triple-helical peptides to direct liposomes to melanoma cells. The molecular information about collagen interactions will further serve as a foundation for computational studies to design small molecules that can interfere with specific interactions or target tumor cells. Intelligent control of collagen biological interactions within a material context will expand the effectiveness of collagen-based drug delivery.

Microbial collagenases: challenges and prospects in production and potential applications in food and nutrition

Microbial collagenases are promising enzymes in view of their extensive industrial and biological applications.

Collagen V Is a Potential Substrate for Clostridial Collagenase G in Pancreatic Islet Isolation

The clostridial collagenases, H and G, play key roles in pancreatic islet isolation. Collagenases digest the peptide bond between Yaa and the subsequent Gly in Gly-Xaa-Yaa repeats. To fully understand the pancreatic islet isolation process, identification of the collagenase substrates in the tissue is very important. Although collagen types I and III were reported as possible substrates for collagenase H, the substrate for collagenase G remains unknown. In this study, collagen type V was focused upon as the target for collagenases. In vitro digestion experiments for collagen type V were performed and analyzed by SDS-PAGE and mass spectrometry. Porcine pancreatic tissues were digested in vitro under three conditions and observed during digestion. The results revealed that collagen type V was only digested by collagenase G and that the digestion was initiated from the N-terminal part. Tissue degradation during porcine islet isolation was only observed in the presence of both collagenases H and G. These findings suggest that collagen type V is one of the substrates for collagenase G. The enzymatic activity of collagenase G appears to be more important for pancreatic islet isolation in large mammals such as pigs and humans.

Diversity, Structures, and Collagen-Degrading Mechanisms of Bacterial Collagenolytic Proteases

Bacterial collagenolytic proteases are important because of their essential role in global collagen degradation and because of their virulence in some human bacterial infections. Bacterial collagenolytic proteases include some metalloproteases of the M9 family from Clostridium or Vibrio strains, some serine proteases distributed in the S1, S8, and S53 families, and members of the U32 family. In recent years, there has been remarkable progress in discovering new bacterial collagenolytic proteases and in investigating the collagen-degrading mechanisms of bacterial collagenolytic proteases. This review provides comprehensive insight into bacterial collagenolytic proteases, especially focusing on the structures and collagen-degrading mechanisms of representative bacterial collagenolytic proteases in each family. The roles of bacterial collagenolytic proteases in human diseases and global nitrogen cycling, together with the biotechnological and medical applications for these proteases, are also briefly discussed.

Structures of three polycystic kidney disease-like domains from Clostridium histolyticum collagenases ColG and ColH

The surface properties and dynamics of PKD-like domains from ColG and ColH differ.

Clostridium histolyticum collagenases ColG and ColH are segmental enzymes that are thought to be activated by Ca²⁺-triggered domain reorientation to cause extensive tissue destruction. The collagenases consist of a collagenase module (s1), a variable number of polycystic kidney disease-like (PKD-like) domains (s2a and s2b in ColH and s2 in ColG) and a variable number of collagen-binding domains (s3 in ColH and s3a and s3b in ColG). The X-ray crystal structures of Ca²⁺-bound holo s2b (1.4 Å resolution, R = 15.0%, R_free = 19.1%) and holo s2a (1.9 Å resolution, R = 16.3%, R_free = 20.7%), as well as of Ca²⁺-free apo s2a (1.8 Å resolution, R = 20.7%, R_free = 27.2%) and two new forms of N-terminally truncated apo s2 (1.4 Å resolution, R = 16.9%, R_free = 21.2%; 1.6 Å resolution, R = 16.2%, R_free = 19.2%), are reported. The structurally similar PKD-like domains resemble the V-set Ig fold. In addition to a conserved β-bulge, the PKD-like domains feature a second bulge that also changes the allegiance of the subsequent β-strand. This β-bulge and the genesis of a Ca²⁺ pocket in the archaeal PKD-like domain suggest a close kinship between bacterial and archaeal PKD-like domains. Different surface properties and indications of different dynamics suggest unique roles for the PKD-like domains in ColG and in ColH. Surface aromatic residues found on ColH s2a-s2b, but not on ColG s2, may provide the weak interaction in the biphasic collagen-binding mode previously found in s2b-s3. B-factor analyses suggest that in the presence of Ca²⁺ the midsection of s2 becomes more flexible but the midsections of s2a and s2b stay rigid. The different surface properties and dynamics of the domains suggest that the PKD-like domains of M9B bacterial collagenase can be grouped into either a ColG subset or a ColH subset. The conserved properties of PKD-like domains in ColG and in ColH include Ca²⁺ binding. Conserved residues not only interact with Ca²⁺, but also position the Ca²⁺-interacting water molecule. Ca²⁺ aligns the N-terminal linker approximately parallel to the major axis of the domain. Ca²⁺ binding also increases stability against heat and guanidine hydrochloride, and may improve the longevity in the extracellular matrix. The results of this study will further assist in developing collagen-targeting vehicles for various signal molecules.

Pharmacokinetics in rats of a long-acting human parathyroid hormone-collagen binding domain peptide construct

The pharmacokinetics of a hybrid peptide consisting of the N-terminal biologically active region of human parathyroid hormone (PTH) linked to a collagen-binding domain (CBD) were evaluated in female Sprague-Dawley rats. The peptide, PTH-CBD, consists of the first 33 amino acids of PTH linked as an extension of the amino acid chain to the CBD peptide derived from ColH collagenase of Clostridium histolyticum. Serum concentrations arising from single dose administration by the subcutaneous and intravenous routes were compared with those measured following route-specific mole equivalent doses of PTH(1-34). Population-based modeling demonstrated similar systemic absorption kinetics and bioavailability for both peptides. Exposure to PTH-CBD was sixfold higher because of a systemic clearance of approximately 20% relative to PTH(1-34); however, these kinetics were consistent with more than 95% of a dose being eliminated from serum within 24 h. Results obtained support continued investigation of PTH-CBD as a bone-targeted anabolic agent for the treatment of postmenopausal osteoporosis.

Proteomic protease specificity profiling of clostridial collagenases reveals their intrinsic nature as dedicated degraders of collagen

Clostridial collagenases are among the most efficient degraders of collagen. Most clostridia are saprophytes and secrete proteases to utilize proteins in their environment as carbon sources; during anaerobic infections, collagenases play a crucial role in host colonization. Several medical and biotechnological applications have emerged utilizing their high collagenolytic efficiency. However, the contribution of the functionally most important peptidase domain to substrate specificity remains unresolved. We investigated the active site sequence specificity of the peptidase domains of collagenase G and H from Clostridium histolyticum and collagenase T from Clostridium tetani. Both prime and non-prime cleavage site specificity were simultaneously profiled using Proteomic Identification of protease Cleavage Sites (PICS), a mass spectrometry-based method utilizing database searchable proteome-derived peptide libraries. For each enzyme we identified > 100 unique-cleaved peptides, resulting in robust cleavage logos revealing collagen-like specificity patterns: a strong preference for glycine in P3 and P1′, proline at P2 and P2′, and a slightly looser specificity at P1, which in collagen is typically occupied by hydroxyproline. This specificity for the classic collagen motifs Gly-Pro-X and Gly-X-Hyp represents a remarkable adaptation considering the complex requirements for substrate unfolding and presentation that need to be fulfilled before a single collagen strand becomes accessible for cleavage.

Biological significance

We demonstrate the striking sequence specificity of a family of clostridial collagenases using proteome derived peptide libraries and PICS, Proteomic Identification of protease Cleavage Sites. In combination with the previously published crystal structures of these proteases, our results represent an important piece of the puzzle in understanding the complex mechanism underlying collagen hydrolysis, and pave the way for the rational design of specific test substrates and selective inhibitors.

This article is part of a Special Issue entitled: Can Proteomics Fill the Gap Between Genomics and Phenotypes?

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Active site specificity profiling of 3 clostridial collagenases—ColG and H from C. histolyticum, and ColT from C. tetani.

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Their high sequence specificity to collagen-like sequence points towards a co-evolution with the mammalian substrate.

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Significant differences to MMPs and a more promiscuous cleavage mechanism facilitating rapid collagenolysis were revealed.

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Human proteome-derived peptide libraries & PICS are suitable for active site specificity profiling of pathogenic proteases.

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Results pave the way for rational design of test substrates and selective inhibitors.

Solution structure of clostridial collagenase H and its calcium-dependent global conformation change

Collagenase H (ColH) from Clostridium histolyticum is a multimodular protein composed of a collagenase module (activator and peptidase domains), two polycystic kidney disease-like domains, and a collagen-binding domain. The interdomain conformation and its changes are very important for understanding the functions of ColH. In this study, small angle x-ray scattering and limited proteolysis were employed to reveal the interdomain arrangement of ColH in solution. The ab initio beads model indicated that ColH adopted a tapered shape with a swollen head. Under calcium-chelated conditions (with EGTA), the overall structure was further elongated. The rigid body model indicated that the closed form of the collagenase module was preferred in solution. The limited proteolysis demonstrated that the protease sensitivity of ColH was significantly increased under the calcium-chelated conditions, and that the digestion mainly occurred in the domain linker regions. Fluorescence measurements with a fluorescent dye were performed with the limited proteolysis products after separation. The results indicated that the limited proteolysis products exhibited fluorescence similar to that of the full-length ColH. These findings suggested that the conformation of full-length ColH in solution is the elongated form, and this form is calcium-dependently maintained at the domain linker regions.