biostudies-literatureUnknown45Ogawa MSmall heat-shock proteins (sHsps) are ATP-independent chaperones whose oligomerization and client capture are regulated by a conserved C-terminal IXI/V motif. Here, we identify and characterize an sHsp from the marine cyanobacterium <i>Picosynechococcus</i> sp. NKBG15041c (NKBG-sHsp), which has an acidic C-terminal extension following IXI/V. We dissect the role of its acidic C-terminal extension using truncation mutants, one with the acidic C-terminal extension deleted (NKBG-sHspΔC), and another with both the acidic C-terminal extension and the IXI/V motif deleted (NKBG-sHspΔΔC). By size-exclusion chromatography by HPLC, NKBG-sHsp and NKBG-sHspΔC existed as large oligomers at 20 °C and reversibly dissociated into smaller species at 50 °C, whereas NKBG-sHspΔΔC remained a small oligomer withBiochemistry and biophysics reports102500https://www.ebi.ac.uk/biostudies/studies/S-EPMC12925178biostudies-literatureStructural and functional characterization of sHsp from the marine cyanobacterium &lt;i&gt;Picosynechococcus&lt;/i&gt; sp. NKBG15041c.PMC12925178Yohda MYamada ANaka WInoue ROgawa MMorishima KSugiyama MfalseStructural and functional characterization of sHsp from the marine cyanobacterium &lt;i&gt;Picosynechococcus&lt;/i&gt; sp. NKBG15041c.Small heat-shock proteins (sHsps) are ATP-independent chaperones whose oligomerization and client capture are regulated by a conserved C-terminal IXI/V motif. Here, we identify and characterize an sHsp from the marine cyanobacterium <i>Picosynechococcus</i> sp. NKBG15041c (NKBG-sHsp), which has an acidic C-terminal extension following IXI/V. We dissect the role of its acidic C-terminal extension using truncation mutants, one with the acidic C-terminal extension deleted (NKBG-sHspΔC), and another with both the acidic C-terminal extension and the IXI/V motif deleted (NKBG-sHspΔΔC). By size-exclusion chromatography by HPLC, NKBG-sHsp and NKBG-sHspΔC existed as large oligomers at 20 °C and reversibly dissociated into smaller species at 50 °C, whereas NKBG-sHspΔΔC remained a small oligomer with2026-01-01T00:00:00Z2026 Mar2026-07-16T18:48:39.603Z2026-07-12T03:08:43.705ZS-EPMC129251784173241610.1016/j.bbrep.2026.102500