Molecular cloning and sequence and 3D models analysis of the Sec61α subunit of protein translocation complex from Penicillium ochrochloron

Abstract

The Sec61α subunit is the core subunit of the protein conducting channel which is required for protein translocation in eukaryotes and prokaryotes. In this study, we cloned a Sec61α subunit from Penicillium ochrochloron (PoSec61α). Sequence and 3D structural model analysis showed that PoSec61α conserved the typical characteristics of eukaryotic and prokaryotic Sec61α subunit homologues. The pore ring known as the constriction point of the channel is formed by seven hydrophobic amino acids. Two methionine residues from transmembrane α-helice 7 (TM7) contribute to the pore ring formation and projected notably to the pore area and narrowed the pore compared with the superposed residues at the corresponding positions in the crystal structures or the 3D models of the Sec61α subunit homologues in archaea or other eukaryotes, respectively. Results reported herein indicate that the pore ring residues differ among Sec61α subunit homologues and two hydrophobic residues in the TM7 contribute to the pore ring formation. [BMB reports 2011; 44(11): 719-724]

Variation in the ribosome interacting loop of the Sec61α from Giardia lamblia

“…Thus, even after the inclusion of prokaryotic sequences, it is evident that with the exception of G. lamblia , the arginine is present in loop 8/9. Sec61α of D. rerio, D. melanogaster, C. elegans and P. ochrochloron , although not included in this study, have been used in published sequence alignments [ 7 , 8 ]; if these are taken into account then the number of organisms increases to 20, of which only one ( G. lamblia ) has K instead of R. Given the high levels of identity of metazoan sequences, we have also checked non-metazoans for which rRNA secondary structure is available ( Cryptococcus neoformans , Chlorella variabilis , Aedes aegypti ) [ 12 ] and observed that even in these cases R is present in loop 8/9 and also G does not occupy either of the two positions in the rRNA under consideration (marked in Additional file 4 ); given the limitation of space, these sequences could not be included in Fig. 1 .…”

“…As previously mentioned in our response to Reviewer 1’s comment, in contrast to the positively-charged residues of loop 6/7, this R residue of loop 8/9 is responsible for specificity. This R residue is present in all Sec61α and SecY orthologues published till date and this is evident even in the sequence alignments published in many of these studies [ 7 , 8 ]. Thus this R residue has even been termed to be ‘universally conserved’ [ 3 ].…”

“…However, the revised manuscript contains several more eukaryotic and also prokaryotic sequences. Additionally, we have also included references to previously-published sequence alignments that include other orthologues as well [ 7 , 8 ].…”

“…The ribosome-interacting R residue in loop 8/9 is present in all prokaryotic and eukaryotic orthologues studied till date, including those from other protists (Fig. 1a ) [ 7 , 8 ]. However, sequence alignment shows that in GlSec61α, K426 is the only positively charged residue in the loop 8/9; thus it is most likely functionally equivalent to the R (Fig.…”

Effects of Dipeptidyl Peptidase-4 Inhibition with MK-0431 on Syngeneic Mouse Islet Transplantation

“…In contrast, DPP-4 inhibitors increase circulating active incretin hormones, GLP-1, and glucose-dependent insulinotropic polypeptide (GIP), by blocking their degradation [11]; thus, they can be beneficial for beta-cells. Previously, many studies have shown DPP-4 inhibitors improved glucose tolerance, insulin secretion, beta-cell glucose responsiveness [16], and insulin sensitivity [16, 17]; promoted beta-cell survival [18–20], islet neogenesis [18, 21], and proliferation [22]; reduced beta-cell death [23]; and preserved beta-cell mass and function [24–26] in diabetic rodents. In contrast, there is limited information regarding the effects of DPP-4 inhibitors on islet transplantation.…”