Posttranslational Modifications in Lens Fiber Connexins Identified by Off-Line-HPLC MALDI-Quadrupole Time-of-Flight Mass Spectrometry
Bibliographic record
Abstract
PURPOSE: Gap junction intercellular communication is necessary for the development and maintenance of the lens. Lens fiber connexins are known to be posttranslationally modified, but little detail is available regarding the nature of some of these modifications and the specific amino acids affected. The purpose of this study was to identify posttranslational modification in the bovine lens fiber connexins, Cx44 and Cx49. METHODS: Crude preparations of bovine lens membranes were isolated by centrifugation. The membrane preparations were digested with trypsin or chymotrypsin, and the entire mixture of peptides produced was separated by reverse-phase high performance liquid chromatography and then analyzed by mass spectrometry and tandem mass spectrometry. RESULTS: Coverage of significant portions of the cytoplasmic domains of both Cx44 and Cx49 were successfully obtained. Several of the Ser and Thr residues in the C-tail of Cx44 were phosphorylated, whereas in Cx49 only Ser phosphorylation was detected; however, in this connexin, the phosphorylated residues were located in both the C-tail and the central cytoplasmic loop. The data also show that the N-terminal Met residue in each connexin is removed and that the newly exposed N termini become acetylated. In addition, cleavage sites were identified in both proteins. CONCLUSIONS: The study documented the nature and locations of several previously unknown posttranslational modifications in lens fiber connexins. This detailed knowledge of the specific posttranslationally modified sites will allow further work to elucidate the mechanisms that different signaling pathways use to regulate connexins in lens fiber cells.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".