The Legacy of Shanti Teresa Lakra and Its Impact on Public Health in the Andaman Islands.

In the Andaman and Nicobar Islands, Shanti Teresa Lakra, a committed Indian medical nurse, has made a major impact on public health. Lakra, who was born in Rangat on May 1, 1972, was motivated to become a nurse by her elder sister. Her work with the Onge tribe has earned her recognition, particularly in the wake of the 2004 tsunami that destroyed their settlements. Lakra has devoted her professional life to enhancing the health of these indigenous people and averting their extinction by working with particularly vulnerable tribal groups. When she started her work, there were just 78 Onge people living there. She worked constantly to improve healthcare and education, and in five years, the population grew to 100. Her effort required overcoming socioeconomic obstacles, linguistic limitations, and the tribe's initial apprehensions. Despite hazardous circumstances, Lakra helped by immunizing the Jarawa tribe during the COVID-19 outbreak. Her efforts have been recognized with prestigious awards, including the Florence Nightingale Award and the Padma Shri. Her legacy is marked by her empowerment of tribal communities, her role as a healthcare role model, and her advancements in public health in remote areas.

Dr. Ratan Chandra Kar: The Journey of the Jarawa Doctor.

 A distinguished physician Dr. Ratan Chandra Kar, born in 1954 in West Bengal, India, is known for his pivotal role in providing healthcare to the Jarawa tribe of the Andaman Islands. He began his service toward the Jarawa tribes in 1998, notably combating a devastating measles outbreak in 1999 that threatened the tribe's existence. Overcoming initial distrust, Dr. Kar earned the tribe's confidence through cultural respect and medical expertise, treating over a hundred patients at the peak of the epidemic. He had established a dedicated Jarawa Ward at Kadamtala Hospital, integrating their traditional practices with modern medicine. For his dedication, Dr. Kar received the Padma Shri in 2023, for contributing significantly to the tribe's growth from 255 to 260 individuals in 1998 to over 560 today. His work stands as a testament to the importance of culturally sensitive healthcare in preserving vulnerable indigenous communities.

Structural and Molecular Basis for Coordination in a Viral DNA Packaging Motor.

Ring NTPases are a class of ubiquitous molecular motors involved in basic biological partitioning processes. dsDNA viruses encode ring ATPases that translocate their genomes to near-crystalline densities within pre-assembled viral capsids. Here, X-ray crystallography, cryoEM, and biochemical analyses of the dsDNA packaging motor in bacteriophage phi29 show how individual subunits are arranged in a pentameric ATPase ring and suggest how their activities are coordinated to translocate dsDNA. The resulting pseudo-atomic structure of the motor and accompanying functional analyses show how ATP is bound in the ATPase active site; identify two DNA contacts, including a potential DNA translocating loop; demonstrate that a trans-acting arginine finger is involved in coordinating hydrolysis around the ring; and suggest a functional coupling between the arginine finger and the DNA translocating loop. The ability to visualize the motor in action illuminates how the different motor components interact with each other and with their DNA substrate.

Structural insights into the architecture of the hyperthermophilic Fusellovirus SSV1.

The structure and assembly of many icosahedral and helical viruses are well-characterized. However, the molecular basis for the unique spindle-shaped morphology of many viruses that infect Archaea remains unknown. To understand the architecture and assembly of these viruses, the spindle-shaped virus SSV1 was examined using cryo-EM, providing the first 3D-structure of a spindle-shaped virus as well as insight into SSV1 biology, assembly and evolution. Furthermore, a geometric framework underlying the distinct spindle-shaped structure is proposed.

Insights into the structure and assembly of the bacteriophage 29 double-stranded DNA packaging motor.

UNLABELLED: The tailed double-stranded DNA (dsDNA) bacteriophage 29 packages its 19.3-kbp genome into a preassembled procapsid structure by using a transiently assembled phage-encoded molecular motor. This process is remarkable considering that compaction of DNA to near-crystalline densities within the confined space of the capsid requires that the packaging motor work against significant entropic, enthalpic, and DNA-bending energies. The motor consists of three phage-encoded components: the dodecameric connector protein gp10, an oligomeric RNA molecule known as the prohead RNA (pRNA), and the homomeric ring ATPase gp16. Although atomic resolution structures of the connector and different pRNA subdomains have been determined, the mechanism of self-assembly and the resulting stoichiometry of the various motor components on the phage capsid have been the subject of considerable controversy. Here a subnanometer asymmetric cryoelectron microscopy (cryo-EM) reconstruction of a connector-pRNA complex at a unique vertex of the procapsid conclusively demonstrates the pentameric symmetry of the pRNA and illuminates the relative arrangement of the connector and the pRNA. Additionally, a combination of biochemical and cryo-EM analyses of motor assembly intermediates suggests a sequence of molecular events that constitute the pathway by which the motor assembles on the head, thereby reconciling conflicting data regarding pRNA assembly and stoichiometry. Taken together, these data provide new insight into the assembly, structure, and mechanism of a complex molecular machine. IMPORTANCE: Viruses consist of a protein shell, or capsid, that protects and surrounds their genetic material. Thus, genome encapsidation is a fundamental and essential step in the life cycle of any virus. In dsDNA viruses, powerful molecular motors essentially pump the viral DNA into a preformed protein shell. This article describes how a viral dsDNA packaging motor self-assembles on the viral capsid and provides insight into its mechanism of action.

FOLD-EM: automated fold recognition in medium- and low-resolution (4-15 Å) electron density maps.

MOTIVATION: Owing to the size and complexity of large multi-component biological assemblies, the most tractable approach to determining their atomic structure is often to fit high-resolution radiographic or nuclear magnetic resonance structures of isolated components into lower resolution electron density maps of the larger assembly obtained using cryo-electron microscopy (cryo-EM). This hybrid approach to structure determination requires that an atomic resolution structure of each component, or a suitable homolog, is available. If neither is available, then the amount of structural information regarding that component is limited by the resolution of the cryo-EM map. However, even if a suitable homolog cannot be identified using sequence analysis, a search for structural homologs should still be performed because structural homology often persists throughout evolution even when sequence homology is undetectable, As macromolecules can often be described as a collection of independently folded domains, one way of searching for structural homologs would be to systematically fit representative domain structures from a protein domain database into the medium/low resolution cryo-EM map and return the best fits. Taken together, the best fitting non-overlapping structures would constitute a 'mosaic' backbone model of the assembly that could aid map interpretation and illuminate biological function. RESULT: Using the computational principles of the Scale-Invariant Feature Transform (SIFT), we have developed FOLD-EM-a computational tool that can identify folded macromolecular domains in medium to low resolution (4-15 Å) electron density maps and return a model of the constituent polypeptides in a fully automated fashion. As a by-product, FOLD-EM can also do flexible multi-domain fitting that may provide insight into conformational changes that occur in macromolecular assemblies.

A three-helix junction is the interface between two functional domains of prohead RNA in 29 DNA packaging.

The double-stranded-DNA bacteriophages employ powerful molecular motors to translocate genomic DNA into preformed capsids during the packaging step in phage assembly. Bacillus subtilis bacteriophage 29 has an oligomeric prohead RNA (pRNA) that is an essential component of its packaging motor. The crystal structure of the pRNA-prohead binding domain suggested that a three-helix junction constitutes both a flexible region and part of a rigid RNA superhelix. Here we define the functional role of the three-helix junction in motor assembly and DNA packaging. Deletion mutagenesis showed that a U-rich region comprising two sides of the junction plays a role in the stable assembly of pRNA to the prohead. The retention of at least two bulged residues in this region was essential for pRNA binding and thereby subsequent DNA packaging. Additional deletions resulted in the loss of the ability of pRNA to multimerize in solution, consistent with the hypothesis that this region provides the flexibility required for pRNA oligomerization and prohead binding. The third side of the junction is part of a large RNA superhelix that spans the motor. The insertion of bases into this feature resulted in a loss of DNA packaging and an impairment of initiation complex assembly. Additionally, cryo-electron microscopy (cryoEM) analysis of third-side insertion mutants showed an increased flexibility of the helix that binds the ATPase, suggesting that the rigidity of the RNA superhelix is necessary for efficient motor assembly and function. These results highlight the critical role of the three-way junction in bridging the prohead binding and ATPase assembly functions of pRNA.

MOTIF-EM: an automated computational tool for identifying conserved regions in CryoEM structures.

UNLABELLED: We present a new, first-of-its-kind, fully automated computational tool MOTIF-EM for identifying regions or domains or motifs in cryoEM maps of large macromolecular assemblies (such as chaperonins, viruses, etc.) that remain conformationally conserved. As a by-product, regions in structures that are not conserved are revealed: this can indicate local molecular flexibility related to biological activity. MOTIF-EM takes cryoEM volumetric maps as inputs. The technique used by MOTIF-EM to detect conserved sub-structures is inspired by a recent breakthrough in 2D object recognition. The technique works by constructing rotationally invariant, low-dimensional representations of local regions in the input cryoEM maps. Correspondences are established between the reduced representations (by comparing them using a simple metric) across the input maps. The correspondences are clustered using hash tables and graph theory is used to retrieve conserved structural domains or motifs. MOTIF-EM has been used to extract conserved domains occurring in large macromolecular assembly maps, including as those of viruses P22 and epsilon 15, Ribosome 70S, GroEL, that remain structurally conserved in different functional states. Our method can also been used to build atomic models for some maps. We also used MOTIF-EM to identify the conserved folds shared among dsDNA bacteriophages HK97, Epsilon 15, and ô29, though they have low-sequence similarity. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Identifying structural motifs in proteins.

In biological macromolecules, structural patterns (motifs) are often repeated across different molecules. Detection of these common motifs in a new molecule can provide useful clues to the functional properties of such a molecule. We formulate the problem of identifying a given structural motif (pattern) in a target protein (example) and discuss the notion of complete matches vis-a-vis partial matches. We describe the precise error criterion that has to be minimized and also discuss different metrics for evaluating the quality of partial matches. Secondly, we present a new polynomial time algorithm for the problem of matching a given motif in a target protein. We also use the sequence and (if available) secondary structure information to annotate the different points in motif and the target protein, thus reducing the search space size. Our algorithm guarantees the detection of a perfect match, if present. Even otherwise, the algorithm computes very good matches. Unlike other methods, the error minimized by our algorithm directly translates to root mean square deviation (RMSD), the most commonly accepted metric for structure matching in biological macromolecules. The algorithm does not involve any preprocessing and is suitable for the detection of both small and large motifs in the target protein. We also present experiments exploring the quality of matches found by the algorithm. We examine its performance in matching (both full and partial) active sites in proteins.