Crystal structure of botulinum neurotoxin subtype A3 cell binding domain in complex with GD1a co‐receptor ganglioside

Abstract

Botulinum neurotoxins (BoNTs) are one of the most toxic proteins known to humans. Their molecular structure is comprised of three essential domains—a cell binding domain (HC), translocation domain and catalytic domain (light chain) . The HC domain facilitates the highly specific binding of BoNTs to the neuronal membrane via a dual‐receptor complex involving a protein receptor and a ganglioside. Variation in activity/toxicity across subtypes of serotype A has been attributed to changes in protein and ganglioside interactions, and their implications are important in the design of novel BoNT‐based therapeutics. Here, we present the structure of BoNT/A3 cell binding domain (HC/A3) in complex with the ganglioside GD1a at 1.75 Å resolution. The structure revealed that six residues interact with the three outermost monosaccharides of GD1a through several key hydrogen bonding interactions. A detailed comparison of structures of HC/A3 with HC/A1 revealed subtle conformational differences at the ganglioside binding site upon carbohydrate binding.

High‐resolution crystal structures of the botulinum neurotoxin binding domains from subtypes A5 and A6

“…Previously, we and others have determined the crystal structures of the binding domains from BoNT subtypes /A1, /A2, /A3 and /A4, and the related /HA alone [13][14][15][16][17], and in complex with various receptors: H C /A1-GT1b [18], H C /A1-SV2C [19,20], H C /A2-SV2C [14,21] and H C /A3-GD1a [22]. Here, we report the crystal structures of the BoNT/A5 and BoNT/A6 receptor-binding domain and compare the binding sites with previous crystal structures of the BoNT/A subtype.…”

Crystal Structures of Botulinum Neurotoxin Subtypes A4 and A5 Cell Binding Domains in Complex with Receptor Ganglioside

“…A total of nine hydrogen bonding interactions were present between H C /A4 and GD1a (Figure 1B) (Table 2)-there was clear electron density for the two terminal nitrogen atoms of Arg 1282 which interact with Sia 5 and Gln 1276. [23]) and H C /A1:GD1a (PDB: 5TPC [22]). Watermediated interactions are indicated by a "-H 2 O molecule (n 1 , n 2 )" where n 1 is the distance between the amino acid residue and the water, and n 2 is the distance between the water and monosaccharide.…”

“…∆ Indicates they are the equivalent water molecule for each structure. Data adapted from [23]. The crystal packing of HC/A4 changes significantly upon binding of GD1a as evidenced by the change in both unit cell dimensions and space group.…”

“…Gangliosides are glycosphingolipids that are often involved in cellular-signalling pathways and are comprised of a membrane anchored hydrophilic lipid tail, and an extracellular oligosaccharide moiety [21]. Previous studies have reported the structures of the binding domain of BoNT/A1 (H C /A1) and BoNT/A3 (H C /A3) in complex with the receptor ganglioside GD1a [22,23], detailing the interactions that occur between the two. These structures reveal that the ganglioside binding site (GBS) is formed by a β-hairpin and loop in the C-terminal subdomain of H C (H CC ).…”

Steering towards success in stormy times: FEBS Open Bio in 2021

“…This article was the subject of our first commentary article [2], and we hope to commission commentaries to accompany other papers of especial significance in the future. Other exciting work across the molecular and cellular life sciences published in FEBS Open Bio this year includes a report of alterations in neuronal development in a mouse model of Timothy syndrome [3], the crystal structure of botulinum neurotoxin subtype A3 cell‐binding domain in complex with the ganglioside GD1a [4], engineered variants of tobacco etch virus protease with enhanced enzymatic activity [5], the discovery that autologous apoptotic neutrophils inhibit inflammatory secretion by dendritic cells [6] and the use of fluorescence microscopy to reveal cooperative binding of cardiac troponin and tropomyosin to filamentous actin [7]. These are but a few of the fascinating studies published this year in the journal.…”