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"E-cadherin adalah protein ekstraseluler transmembran dan calciumdependent pada adhesi sel-sel. E-cadherin memiliki fungsi penting dalam pembentukan penghubung protein adheren pada jembatan interselular seperti mukosa usus dan sawar darah otak (blood brain barrier, BBB). Peptida yang berasal dari sekuens lestari EC1 memiliki aktivitas yang berpotensi untuk memodulasi jembatan adheren di sawar darah otak. Peptida telah menunjukkan kemampuan mereka untuk menghantarkan molekul obat di sawar darah otak dan mengatasi penghalang biologis seperti: enzim metabolisme, tight junction dan efflux pump yang mencegah transportasi obat dari sirkulasi sistemik ke otak. Dalam modulasi sawar darah otak, peptida menghambat interaksi cadherincadherin. Peptida selektif diperlukan untuk meningkatkan modulasi E-cadherin. Struktur EC1 domain digunakan dalam merancang peptida selektif untuk memodulasi E-cadherin. Dalam struktur tingkat atom, spektroskopi NMR cair adalah instrument yang sangat reliabel dalam mengelusidasi struktur, konformasi dan dinamika. Dalam studi ini, kami telah berhasil menerapkan teknik NMR tiga dimensi untuk menentukan residu EC1 yang berlabel isotop 1H, 13C, dan 15N. Sebanyak 90% asam amino dalam EC1 telah berhasil ditentukan. Hasil penentuan asam amino EC1 tersebut kemudian digunakan sebagai sidik jari untuk menemukan pergeseran resonansi kimia yang mungkin terjadi sebagai tanda adanya interaksi ikatan antara asam amino EC1 dengan molekul peptida. Metode titrasi peptida HAV6 (Ac-SHAVSS-NH2) dan ADTC5 (Ac-CDTPPVC-NH2) telah digunakan untuk mengetahui situs ikatan asam amino EC1 spesifik dengan peptida. Hasilnya menunjukkan bahwa residu Ile-4 dan Asp-103 pada domain EC1 menunjukkan perubahan yang paling besar dibandingkan dengan residu lainnya. Berdasarkan nilai CSP (Chemical Shift Perturbation), residu ini diinvestigasi lebih lanjut untuk melihat interaksinya dengan peptida. Kami menggunakan struktur domain E-cadherin 1 dari database PDB struktur kristal difraksi sinar X sebagai model protein. Struktur peptida didesain menggunakan program pemodelan struktur 2D dan 3D. Komputasi docking digunakan untuk mencari konformasi dengan probabilitas tertinggi dalam berikatan dengan residu protein. Dengan mentransformasi nilai CSP ke dalam studi docking, residu Ile-4 dan Asp-103 menunjukkan adanya perbedaan dalam konformasi dan ikatan kimia yang terlibat serta afinitas terbaik dengan peptida HAV6 dan ADTC5. Hasil penelitian ini diharapkan dapat digunakan sebagai model untuk mendesain peptida kecil dengan kemampuan affinitas lebih tinggi dengan EC1 untuk meningkatkan penghantaran obat melalui jalur mukosa usus dan sawar darah otak.

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E-cadherin is an extracellular protein transmembrane and calciumdependent of cell-cell adhesion. E-cadherin has an important function in formation of adherens junction in the intercellular junction of biological barriers such as the intestinal mucosa and the blood brain barrier (BBB). Peptides derived from the conserved region of EC1 have highly potential activity to modulate the adherens junctions in BBB. Peptides have shown their ability to deliver the drug molecules across the BBB and overcome drug delivery issues in BBB such as metabolism enzymes, tight junction and efflux pump that prevent drug transport from the systemic circulation into the brain. In modulating the BBB, peptides inhibit cadherin-cadherin interactions. The selective peptides are necessary required to improve E-cadherin modulation. Elucidation of EC1 domain structure would provide information in designing the peptides selectively to modulate E-cadherin. In atomic level structure, solution NMR spectroscopy is a valuable tool to examine the changes in structure, conformation and dynamics. In this study, we have successfully applied the three-dimensional NMR techniques to determine the 1H, 13C, and 15N backbone assignments of EC1 in the 13C-15N-labeled EC1 solution structure study. Approximately 90% of EC1 residues have been successfully assigned. The EC1 backbone assignment then was used as a fingerprint to find the resonance chemical shift of possible EC1-peptide binding sites by titrating the peptide in solution. Titration using HAV6 (Ac-SHAVSSNH2) peptide and ADTC5 (Ac-CDTPPVC-NH2) into 15N-labeled-EC1 solution have been undertaken by two-dimensional NMR to resolve the binding site of the EC1-peptide complex by monitoring perturbations in the backbone amides.

Our study to investigate the detail mechanism and interaction sites has been done. Residue Ile-4 and Asp-103 of EC1 domain showed the most changes over other residues based on CSP value. These residues were further investigated its specific interaction with the peptides. . We used human E-cadherin 1 domain X-ray structure from PDB as a protein model in docking. Peptide structures were drawn with the 2D and 3D structure builder program. Computational docking was used to search the high probability conformers to bind the protein residue. By transforming CSP value to docking study we could find that residue Ile-4 and Asp-103 showed distinct conformations with favorable binding modes, chemical bonds involved and the best affinities with HAV6 and ADTC5 peptides. Furthermore, the result will be used as model to design small peptides that have higher binding capability to the EC1 for improving drug delivery through the intestinal mucosa and the blood brain barrier."

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