Vomiting as a Presenting Symptom of Infantile Vitamin B12 Deficiency.

An 8-month-old, exclusively breastfed girl presented with a five-month history of vomiting with subsequent failure to thrive and lethargy. Family history was notable for the maternal history of gastroschisis. Mother had no dietary restrictions and had successfully breastfed multiple children for >12 months without issue. Initial evaluation was notable for macrocytic anemia. Subsequent serum B12 levels were undetectable. Upon further questioning, the mother had significant bowel resection as an infant due to complications of gastroschisis. Maternal serum B12 levels were also undetectable. The infant's symptoms resolved with supplementation.

The evolutionarily conserved C-terminal peptide of troponin I is an independently configured regulatory structure to function as a myofilament Ca2+-desensitizer.

The C-terminal end segment of troponin subunit I (TnI) is a structure highly conserved among the three muscle type-specific isoforms and across vertebrate species. Partial deletion or point mutation in this segment impairs cardiac muscle relaxation. In the present study, we characterized the C-terminal 27 amino acid peptide of human cardiac TnI (HcTnI-C27) for its role in modulating muscle contractility. Biologically or chemically synthesized HcTnI-C27 peptide retains an epitope structure in physiological solutions similarly to that in intact TnI as recognized by an anti-TnI C-terminus monoclonal antibody (mAb TnI-1). Protein binding studies found that HcTnI-C27 retains the binding affinity for tropomyosin as previously shown with intact cardiac TnI. A restrictive cardiomyopathy mutation R192H in this segment abolishes the bindings to mAb TnI-1 and tropomyosin, demonstrating a pathogenic loss of function. Contractility studies using skinned muscle preparations demonstrated that addition of HcTnI-C27 peptide reduces the Ca2+-sensitivity of myofibrils without decreasing maximum force production. The results indicate that the C-terminal end segment of TnI is a regulatory element of troponin, which retains the native configuration in the form of free peptide to confer an effect on myofilament Ca2+-desensitization. Without negative inotropic impact, this short peptide may be developed into a novel reagent to selectively facilitate cardiac muscle relaxation at the activated state as a potential treatment for heart failure.

Antibody Epitope Analysis to Investigate Folded Structure, Allosteric Conformation, and Evolutionary Lineage of Proteins.

BACKGROUND: Study of folded structure of proteins provides insights into their biological functions, conformational dynamics and molecular evolution. Current methods of elucidating folded structure of proteins are laborious, low-throughput, and constrained by various limitations. Arising from these methods is the need for a sensitive, quantitative, rapid and high-throughput method not only analysing the folded structure of proteins, but also to monitor dynamic changes under physiological or experimental conditions. OBJECTIVES: In this focused review, we outline the foundation and limitations of current protein structure-determination methods prior to discussing the advantages of an emerging antibody epitope analysis for applications in structural, conformational and evolutionary studies of proteins. METHODS: We discuss the application of this method using representative examples in monitoring allosteric conformation of regulatory proteins and the determination of the evolutionary lineage of related proteins and protein isoforms. RESULTS: The versatility of the method described herein is validated by the ability to modulate a variety of assay parameters to meet the needs of the user in order to monitor protein conformation. Furthermore, the assay has been used to clarify the lineage of troponin isoforms beyond what has been depicted by sequence homology alone, demonstrating the nonlinear evolutionary relationship between primary structure and tertiary structure of proteins. CONCLUSION: The antibody epitope analysis method is a highly adaptable technique of protein conformation elucidation, which can be easily applied without the need for specialized equipment or technical expertise. When applied in a systematic and strategic manner, this method has the potential to reveal novel and biomedically meaningful information for structure-function relationship and evolutionary lineage of proteins.