Dataset Information

Structure of the recombinant BPTI/Kunitz-type inhibitor rShPI-1A from the marine invertebrate Stichodactyla helianthus.

ABSTRACT: The BPTI/Kunitz-type inhibitor family includes several extremely potent serine protease inhibitors. To date, the inhibitory mechanisms have only been studied for mammalian inhibitors. Here, the first crystal structure of a BPTI/Kunitz-type inhibitor from a marine invertebrate (rShPI-1A) is reported to 2.5?Å resolution. Crystallization of recombinant rShPI-1A required the salt-induced dissociation of a trypsin complex that was previously formed to avoid intrinsic inhibitor aggregates in solution. The rShPI-1A structure is similar to the NMR structure of the molecule purified from the natural source, but allowed the assignment of disulfide-bridge chiralities and the detection of an internal stabilizing water network. A structural comparison with other BPTI/Kunitz-type canonical inhibitors revealed unusual ? angles at positions 17 and 30 to be a particular characteristic of the family. A significant clustering of ? and ? angle values in the glycine-rich remote fragment near the secondary binding loop was additionally identified, but its impact on the specificity of rShPI-1A and similar molecules requires further study.

SUBMITTER: Garcia-Fernandez R

PROVIDER: S-EPMC3515366 | biostudies-literature | 2012 Nov

REPOSITORIES: biostudies-literature

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Structure of the recombinant BPTI/Kunitz-type inhibitor rShPI-1A from the marine invertebrate Stichodactyla helianthus.

García-Fernández Rossana R Pons Tirso T Meyer Arne A Perbandt Markus M González-González Yamile Y Gil Dayrom D de los Angeles Chávez María M Betzel Christian C Redecke Lars L

Acta crystallographica. Section F, Structural biology and crystallization communications 20121026 Pt 11

The BPTI/Kunitz-type inhibitor family includes several extremely potent serine protease inhibitors. To date, the inhibitory mechanisms have only been studied for mammalian inhibitors. Here, the first crystal structure of a BPTI/Kunitz-type inhibitor from a marine invertebrate (rShPI-1A) is reported to 2.5 Å resolution. Crystallization of recombinant rShPI-1A required the salt-induced dissociation of a trypsin complex that was previously formed to avoid intrinsic inhibitor aggregates in solution. ...[more]

PMID: 23143234

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Project description:BACKGROUND: Recent studies of the tick saliva transcriptome have revealed the profound role of salivary proteins in blood feeding. Kunitz/BPTI proteins are abundant in the salivary glands of ticks and perform multiple functions in blood feeding, such as inhibiting blood coagulation, regulating host blood supply and disrupting host angiogenesis. However, Kunitz/BPTI proteins in soft and hard ticks have different functions and molecular mechanisms. How these differences emerged and whether they are associated with the evolution of long-term blood feeding in hard ticks remain unknown. RESULTS: In this study, the evolution, expansion and expression of Kunitz/BPTI family in Ixodes scapularis were investigated. Single- and multi-domain Kunitz/BPTI proteins have similar gene structures. Single-domain proteins were classified into three groups (groups I, II and III) based on their cysteine patterns. Group I represents the ancestral branch of the Kunitz/BPTI family, and members of this group function as serine protease inhibitors. The group I domain was used as a module to create multi-domain proteins in hard ticks after the split between hard and soft ticks. However, groups II and III, which evolved from group I, are only present and expanded in the genus Ixodes. These lineage-specific expanded genes exhibit significantly higher expression during long-term blood feeding in Ixodes scapularis. Interestingly, functional site analysis suggested that group II proteins lost the ability to inhibit serine proteases and evolved a new function of modulating ion channels. Finally, evolutionary analyses revealed that the expansion and diversification of the Kunitz/BPTI family in the genus Ixodes were driven by positive selection. CONCLUSIONS: These results suggest that the differences in the Kunitz/BPTI family between soft and hard ticks may be linked to the evolution of long-term blood feeding in hard ticks. In Ixodes, the lineage-specific expanded genes (Group II and III) lost the ancient function of inhibiting serine proteases and evolved new functions to adapt to long-term blood feeding. Therefore, these genes may play a profound role in the long-term blood feeding of hard ticks. Based our analysis, we propose that the six genes identified in our study may be candidate target genes for tick control.

Dataset Information

Structure of the recombinant BPTI/Kunitz-type inhibitor rShPI-1A from the marine invertebrate Stichodactyla helianthus.

Publications

Structure of the recombinant BPTI/Kunitz-type inhibitor rShPI-1A from the marine invertebrate Stichodactyla helianthus.

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